BASELINE: Update Chromium to 83.0.4103.122

Change-Id: Ie3a82f5bb0076eec2a7c6a6162326b4301ee291e Reviewed-by: Michael Brüning <michael.bruning@qt.io>
author: Allan Sandfeld Jensen <allan.jensen@qt.io> 2020-07-16 11:45:35 +0200
committer: Allan Sandfeld Jensen <allan.jensen@qt.io> 2020-07-17 08:59:23 +0000
commit: 552906b0f222c5d5dd11b9fd73829d510980461a (patch)
tree: 3a11e6ed0538a81dd83b20cf3a4783e297f26d91 /chromium/components/feed
parent: 1b05827804eaf047779b597718c03e7d38344261 (diff)
download: qtwebengine-chromium-552906b0f222c5d5dd11b9fd73829d510980461a.tar.gz
149 files changed, 8760 insertions, 579 deletions
diff --git a/chromium/components/feed/BUILD.gn b/chromium/components/feed/BUILD.gn
index 4cc4b9650dc..b5c7af06453 100644
--- a/chromium/components/feed/BUILD.gn
+++ b/chromium/components/feed/BUILD.gn
@@ -19,15 +19,15 @@ static_library("feature_list") {
     "feed_feature_list.h",
   ]
 
-  deps = [
-    "//base",
-  ]
+  deps = [ "//base" ]
 }
 
 source_set("unit_tests") {
   testonly = true
   deps = [
     "core:core_unit_tests",
+    "core/v2:core_unit_tests",
+    "//components/feed/core/common:core_common_unit_tests",
   ]
 
   if (!is_ios) {
diff --git a/chromium/components/feed/content/BUILD.gn b/chromium/components/feed/content/BUILD.gn
index 86922f20148..2c66bca0be8 100644
--- a/chromium/components/feed/content/BUILD.gn
+++ b/chromium/components/feed/content/BUILD.gn
@@ -28,9 +28,7 @@ source_set("feed_content") {
 
 source_set("content_unit_tests") {
   testonly = true
-  sources = [
-    "feed_offline_host_unittest.cc",
-  ]
+  sources = [ "feed_offline_host_unittest.cc" ]
 
   deps = [
     ":feed_content",
diff --git a/chromium/components/feed/core/BUILD.gn b/chromium/components/feed/core/BUILD.gn
index 01ca5f49ed1..a2e1aa17519 100644
--- a/chromium/components/feed/core/BUILD.gn
+++ b/chromium/components/feed/core/BUILD.gn
@@ -28,26 +28,22 @@ source_set("feed_core") {
     "feed_networking_host.h",
     "feed_scheduler_host.cc",
     "feed_scheduler_host.h",
-    "pref_names.cc",
-    "pref_names.h",
-    "refresh_throttler.cc",
-    "refresh_throttler.h",
     "time_serialization.cc",
     "time_serialization.h",
-    "user_classifier.cc",
-    "user_classifier.h",
   ]
 
   public_deps = [
     "//base",
     "//components/feed:feature_list",
     "//components/feed/core/proto",
+    "//components/feed/core/shared_prefs:feed_shared_prefs",
     "//components/leveldb_proto",
     "//net",
     "//ui/base/mojom:mojom",
   ]
 
   deps = [
+    "//components/feed/core/common:feed_core_common",
     "//components/prefs",
     "//components/signin/public/identity_manager",
     "//components/variations",
@@ -63,9 +59,7 @@ source_set("feed_core") {
 
 if (is_android) {
   java_cpp_enum("feed_core_java_enums_srcjar") {
-    sources = [
-      "feed_scheduler_host.h",
-    ]
+    sources = [ "feed_scheduler_host.h" ]
   }
 }
 
@@ -79,14 +73,13 @@ source_set("core_unit_tests") {
     "feed_logging_metrics_unittest.cc",
     "feed_networking_host_unittest.cc",
     "feed_scheduler_host_unittest.cc",
-    "refresh_throttler_unittest.cc",
-    "user_classifier_unittest.cc",
   ]
 
   deps = [
     ":feed_core",
     "//base",
     "//base/test:test_support",
+    "//components/feed/core/common:feed_core_common",
     "//components/leveldb_proto:test_support",
     "//components/prefs:test_support",
     "//components/signin/public/identity_manager:test_support",
diff --git a/chromium/components/feed/core/common/BUILD.gn b/chromium/components/feed/core/common/BUILD.gn
new file mode 100644
index 00000000000..61b32e02cb4
--- /dev/null
+++ b/chromium/components/feed/core/common/BUILD.gn
@@ -0,0 +1,51 @@
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+if (is_android) {
+  import("//build/config/android/rules.gni")
+}
+
+source_set("feed_core_common") {
+  sources = [
+    "enums.h",
+    "pref_names.cc",
+    "pref_names.h",
+    "refresh_throttler.cc",
+    "refresh_throttler.h",
+    "user_classifier.cc",
+    "user_classifier.h",
+  ]
+  deps = [ "//components/prefs" ]
+
+  public_deps = [
+    "//base",
+    "//components/feed:feature_list",
+    "//components/feed/core/proto",
+  ]
+}
+
+source_set("core_common_unit_tests") {
+  testonly = true
+  sources = [
+    "refresh_throttler_unittest.cc",
+    "user_classifier_unittest.cc",
+  ]
+
+  deps = [
+    ":feed_core_common",
+    "//base",
+    "//base/test:test_support",
+    "//components/leveldb_proto:test_support",
+    "//components/prefs:test_support",
+    "//components/signin/public/identity_manager:test_support",
+    "//components/variations:test_support",
+    "//components/web_resource",
+    "//net:test_support",
+    "//services/network:test_support",
+    "//services/network/public/cpp",
+    "//services/network/public/mojom",
+    "//third_party/zlib/google:compression_utils",
+    "//ui/gfx:test_support",
+  ]
+}
diff --git a/chromium/components/feed/core/common/README.md b/chromium/components/feed/core/common/README.md
new file mode 100644
index 00000000000..09538074edb
--- /dev/null
+++ b/chromium/components/feed/core/common/README.md
@@ -0,0 +1 @@
+This directory contains code common to feed v2 and v1.
diff --git a/chromium/components/feed/core/common/enums.h b/chromium/components/feed/core/common/enums.h
new file mode 100644
index 00000000000..23fc0ea27c1
--- /dev/null
+++ b/chromium/components/feed/core/common/enums.h
@@ -0,0 +1,52 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_COMMON_ENUMS_H_
+#define COMPONENTS_FEED_CORE_COMMON_ENUMS_H_
+
+// This file contains enumerations common to Feed v1 and v2.
+
+namespace feed {
+
+// The TriggerType enum specifies values for the events that can trigger
+// refreshing articles. When adding values, be certain to also update the
+// corresponding definition in enums.xml.
+enum class TriggerType {
+  kNtpShown = 0,
+  kForegrounded = 1,
+  kFixedTimer = 2,
+  kMaxValue = kFixedTimer
+};
+
+// Different groupings of usage. A user will belong to exactly one of these at
+// any given point in time. Can change at runtime.
+enum class UserClass {
+  kRareSuggestionsViewer,      // Almost never opens surfaces that show
+                               // suggestions, like the NTP.
+  kActiveSuggestionsViewer,    // Frequently shown suggestions, but does not
+                               // usually open them.
+  kActiveSuggestionsConsumer,  // Frequently opens news articles.
+};
+
+// Enum for the status of the refresh, reported through UMA.
+// If any new values are added, update FeedSchedulerRefreshStatus in
+// enums.xml.
+// These values are persisted to logs. Entries should not be renumbered and
+// numeric values should never be reused.
+enum class ShouldRefreshResult {
+  kShouldRefresh = 0,
+  kDontRefreshOutstandingRequest = 1,
+  kDontRefreshTriggerDisabled = 2,
+  kDontRefreshNetworkOffline = 3,
+  kDontRefreshEulaNotAccepted = 4,
+  kDontRefreshArticlesHidden = 5,
+  kDontRefreshRefreshSuppressed = 6,
+  kDontRefreshNotStale = 7,
+  kDontRefreshRefreshThrottled = 8,
+  kMaxValue = kDontRefreshRefreshThrottled,
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_COMMON_ENUMS_H_
diff --git a/chromium/components/feed/core/pref_names.cc b/chromium/components/feed/core/common/pref_names.cc
index d6d779d20dc..1abd2fc4d1d 100644
--- a/chromium/components/feed/core/pref_names.cc
+++ b/chromium/components/feed/core/common/pref_names.cc
@@ -2,19 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/feed/core/pref_names.h"
+#include "components/feed/core/common/pref_names.h"
 
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/user_classifier.h"
 #include "components/prefs/pref_registry_simple.h"
 
 namespace feed {
 
 namespace prefs {
 
-const char kEnableSnippets[] = "ntp_snippets.enable";
-
-const char kArticlesListVisible[] = "ntp_snippets.list_visible";
-
 const char kBackgroundRefreshPeriod[] = "feed.background_refresh_period";
 
 const char kLastFetchAttemptTime[] = "feed.last_fetch_attempt";
@@ -35,6 +31,11 @@ const char kUserClassifierLastTimeToUseSuggestions[] =
 const char kHostOverrideHost[] = "feed.host_override.host";
 const char kHostOverrideBlessNonce[] = "feed.host_override.bless_nonce";
 
+const char kThrottlerRequestCountListPrefName[] =
+    "feedv2.request_throttler.request_counts";
+const char kThrottlerLastRequestTime[] =
+    "feedv2.request_throttler.last_request_time";
+
 }  // namespace prefs
 
 void RegisterProfilePrefs(PrefRegistrySimple* registry) {
@@ -45,6 +46,9 @@ void RegisterProfilePrefs(PrefRegistrySimple* registry) {
   registry->RegisterTimePref(prefs::kLastFetchAttemptTime, base::Time());
   registry->RegisterTimeDeltaPref(prefs::kBackgroundRefreshPeriod,
                                   base::TimeDelta());
+  registry->RegisterListPref(feed::prefs::kThrottlerRequestCountListPrefName);
+  registry->RegisterTimePref(feed::prefs::kThrottlerLastRequestTime,
+                             base::Time());
   UserClassifier::RegisterProfilePrefs(registry);
 }
 
diff --git a/chromium/components/feed/core/pref_names.h b/chromium/components/feed/core/common/pref_names.h
index 85898c1a03d..f3bc8f04ccb 100644
--- a/chromium/components/feed/core/pref_names.h
+++ b/chromium/components/feed/core/common/pref_names.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_FEED_CORE_PREF_NAMES_H_
-#define COMPONENTS_FEED_CORE_PREF_NAMES_H_
+#ifndef COMPONENTS_FEED_CORE_COMMON_PREF_NAMES_H_
+#define COMPONENTS_FEED_CORE_COMMON_PREF_NAMES_H_
 
 class PrefRegistrySimple;
 
@@ -11,14 +11,6 @@ namespace feed {
 
 namespace prefs {
 
-// The pref name for whether suggested articles is allowed at all. When false,
-// all Feed Java objects will be destroyed/nulled. Typically set by policy.
-extern const char kEnableSnippets[];
-
-// The pref name for whether the suggested articles section is expanded or
-// collapsed. Only when it is expanded are the articles themselves visible.
-extern const char kArticlesListVisible[];
-
 // The pref name for the period of time between background refreshes.
 extern const char kBackgroundRefreshPeriod[];
 
@@ -50,10 +42,17 @@ extern const char kHostOverrideHost[];
 // The pref name for the feed host override auth token.
 extern const char kHostOverrideBlessNonce[];
 
+// The following prefs are used only by v2.
+
+// The pref name for the request throttler counts.
+extern const char kThrottlerRequestCountListPrefName[];
+// The pref name for the request throttler's last request time.
+extern const char kThrottlerLastRequestTime[];
+
 }  // namespace prefs
 
 void RegisterProfilePrefs(PrefRegistrySimple* registry);
 
 }  // namespace feed
 
-#endif  // COMPONENTS_FEED_CORE_PREF_NAMES_H_
+#endif  // COMPONENTS_FEED_CORE_COMMON_PREF_NAMES_H_
diff --git a/chromium/components/feed/core/refresh_throttler.cc b/chromium/components/feed/core/common/refresh_throttler.cc
index 223ffd34293..b121d1ac1e6 100644
--- a/chromium/components/feed/core/refresh_throttler.cc
+++ b/chromium/components/feed/core/common/refresh_throttler.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/feed/core/refresh_throttler.h"
+#include "components/feed/core/common/refresh_throttler.h"
 
 #include <limits>
 #include <set>
@@ -14,7 +14,7 @@
 #include "base/metrics/histogram_base.h"
 #include "base/strings/stringprintf.h"
 #include "base/time/clock.h"
-#include "components/feed/core/pref_names.h"
+#include "components/feed/core/common/pref_names.h"
 #include "components/feed/feed_feature_list.h"
 #include "components/prefs/pref_service.h"
 
@@ -34,23 +34,22 @@ enum class RequestStatus {
 // When adding a new type here, extend also the "RequestThrottlerTypes"
 // <histogram_suffixes> in histograms.xml with the |name| string. First value in
 // the pair is the name, second is the default requests per day.
-std::pair<std::string, int> GetThrottlerParams(
-    UserClassifier::UserClass user_class) {
+std::pair<std::string, int> GetThrottlerParams(UserClass user_class) {
   switch (user_class) {
-    case UserClassifier::UserClass::kRareSuggestionsViewer:
+    case UserClass::kRareSuggestionsViewer:
       return {"SuggestionFetcherRareNTPUser", 5};
-    case UserClassifier::UserClass::kActiveSuggestionsViewer:
+    case UserClass::kActiveSuggestionsViewer:
       return {"SuggestionFetcherActiveNTPUser", 20};
-    case UserClassifier::UserClass::kActiveSuggestionsConsumer:
+    case UserClass::kActiveSuggestionsConsumer:
       return {"SuggestionFetcherActiveSuggestionsConsumer", 20};
   }
 }
 
 }  // namespace
 
-RefreshThrottler::RefreshThrottler(UserClassifier::UserClass user_class,
+RefreshThrottler::RefreshThrottler(UserClass user_class,
                                    PrefService* pref_service,
-                                   base::Clock* clock)
+                                   const base::Clock* clock)
     : pref_service_(pref_service), clock_(clock) {
   DCHECK(pref_service);
   DCHECK(clock);
diff --git a/chromium/components/feed/core/refresh_throttler.h b/chromium/components/feed/core/common/refresh_throttler.h
index 69c37ee249f..d8547991fe9 100644
--- a/chromium/components/feed/core/refresh_throttler.h
+++ b/chromium/components/feed/core/common/refresh_throttler.h
@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_FEED_CORE_REFRESH_THROTTLER_H_
-#define COMPONENTS_FEED_CORE_REFRESH_THROTTLER_H_
+#ifndef COMPONENTS_FEED_CORE_COMMON_REFRESH_THROTTLER_H_
+#define COMPONENTS_FEED_CORE_COMMON_REFRESH_THROTTLER_H_
 
 #include <string>
 
 #include "base/macros.h"
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/user_classifier.h"
 
 class PrefService;
 
@@ -28,9 +28,9 @@ namespace feed {
 //  - "NewTabPage.RequestThrottler.PerDay_|name|" - the daily count of requests.
 class RefreshThrottler {
  public:
-  RefreshThrottler(UserClassifier::UserClass user_class,
+  RefreshThrottler(UserClass user_class,
                    PrefService* pref_service,
-                   base::Clock* clock);
+                   const base::Clock* clock);
 
   // Returns whether quota is available for another request, persists the usage
   // of said quota, and reports this information to UMA.
@@ -51,7 +51,7 @@ class RefreshThrottler {
   PrefService* pref_service_;
 
   // Used to access current time, injected for testing.
-  base::Clock* clock_;
+  const base::Clock* clock_;
 
   // The name used by this throttler, based off UserClass, which will be used as
   // a suffix when constructing histogram or finch param names.
@@ -71,4 +71,4 @@ class RefreshThrottler {
 
 }  // namespace feed
 
-#endif  // COMPONENTS_FEED_CORE_REFRESH_THROTTLER_H_
+#endif  // COMPONENTS_FEED_CORE_COMMON_REFRESH_THROTTLER_H_
diff --git a/chromium/components/feed/core/refresh_throttler_unittest.cc b/chromium/components/feed/core/common/refresh_throttler_unittest.cc
index 7b26fb64656..74ab0d46e9b 100644
--- a/chromium/components/feed/core/refresh_throttler_unittest.cc
+++ b/chromium/components/feed/core/common/refresh_throttler_unittest.cc
@@ -2,15 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/feed/core/refresh_throttler.h"
+#include "components/feed/core/common/refresh_throttler.h"
 
 #include <limits>
 #include <memory>
 
 #include "base/test/scoped_feature_list.h"
 #include "base/test/simple_test_clock.h"
-#include "components/feed/core/pref_names.h"
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/common/user_classifier.h"
 #include "components/feed/feed_feature_list.h"
 #include "components/prefs/testing_pref_service.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -38,8 +38,7 @@ class RefreshThrottlerTest : public testing::Test {
         {{"quota_SuggestionFetcherActiveNTPUser", "2"}});
 
     throttler_ = std::make_unique<RefreshThrottler>(
-        UserClassifier::UserClass::kActiveSuggestionsViewer, &test_prefs_,
-        &test_clock_);
+        UserClass::kActiveSuggestionsViewer, &test_prefs_, &test_clock_);
   }
 
  protected:
diff --git a/chromium/components/feed/core/user_classifier.cc b/chromium/components/feed/core/common/user_classifier.cc
index c3061321216..e286833e528 100644
--- a/chromium/components/feed/core/user_classifier.cc
+++ b/chromium/components/feed/core/common/user_classifier.cc
@@ -2,10 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/user_classifier.h"
 
 #include <algorithm>
 #include <cfloat>
+#include <cmath>
 #include <string>
 
 #include "base/metrics/histogram_macros.h"
@@ -13,11 +14,9 @@
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/time/clock.h"
-#include "components/feed/core/pref_names.h"
-#include "components/feed/feed_feature_list.h"
+#include "components/feed/core/common/pref_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
-#include "components/variations/variations_associated_data.h"
 
 namespace feed {
 
@@ -25,30 +24,27 @@ namespace {
 
 // The discount rate for computing the discounted-average rates. Must be
 // strictly larger than 0 and strictly smaller than 1!
-const double kDiscountRatePerDay = 0.25;
-const char kDiscountRatePerDayParam[] = "user_classifier_discount_rate_per_day";
+constexpr double kDiscountRatePerDay = 0.25;
+static_assert(kDiscountRatePerDay > 0 && kDiscountRatePerDay < 1,
+              "invalid value");
+// Compute discount_rate_per_hour such that
+//   kDiscountRatePerDay = 1 - e^{-kDiscountRatePerHour * 24}.
+const double kDiscountRatePerHour =
+    std::log(1.0 / (1.0 - kDiscountRatePerDay)) / 24.0;
 
 // Never consider any larger interval than this (so that extreme situations such
 // as losing your phone or going for a long offline vacation do not skew the
 // average too much).
-// When overriding via variation parameters, it is better to use smaller values
-// than |kMaxHours| as this it the maximum value reported in the histograms.
 const double kMaxHours = 7 * 24;
-const char kMaxHoursParam[] = "user_classifier_max_hours";
 
 // Ignore events within |kMinHours| hours since the last event (|kMinHours| is
 // the length of the browsing session where subsequent events of the same type
 // do not count again).
 const double kMinHours = 0.5;
-const char kMinHoursParam[] = "user_classifier_min_hours";
 
 // Classification constants.
 const double kActiveConsumerClicksAtLeastOncePerHours = 96;
-const char kActiveConsumerClicksAtLeastOncePerHoursParam[] =
-    "user_classifier_active_consumer_clicks_at_least_once_per_hours";
 const double kRareUserViewsAtMostOncePerHours = 96;
-const char kRareUserViewsAtMostOncePerHoursParam[] =
-    "user_classifier_rare_user_views_at_most_once_per_hours";
 
 // Histograms for logging the estimated average hours to next event. During
 // launch these must match legacy histogram names.
@@ -61,67 +57,35 @@ const char kHistogramAverageHoursToUseSuggestions[] =
 const UserClassifier::Event kEvents[] = {
     UserClassifier::Event::kSuggestionsViewed,
     UserClassifier::Event::kSuggestionsUsed};
-
-// Arrays of pref names, indexed by Event's int value.
-const char* kRateKeys[] = {prefs::kUserClassifierAverageSuggestionsViwedPerHour,
-                           prefs::kUserClassifierAverageSuggestionsUsedPerHour};
-const char* kLastTimeKeys[] = {prefs::kUserClassifierLastTimeToViewSuggestions,
-                               prefs::kUserClassifierLastTimeToUseSuggestions};
-
-// Default lengths of the intervals for new users for the events.
-const double kInitialHoursBetweenEvents[] = {24, 120};
-const char* kInitialHoursBetweenEventsParams[] = {
-    "user_classifier_default_interval_suggestions_viewed",
-    "user_classifier_default_interval_suggestions_used"};
-
-// This verifies that each of the arrays has exactly the same number of values
-// as the number of enum values in UserClassifier::Event. These arrays are all
-// indexed by the integer value of UserClassifier::Event values.
 static_assert(base::size(kEvents) ==
-                      static_cast<int>(UserClassifier::Event::kMaxValue) + 1 &&
-                  base::size(kRateKeys) ==
-                      static_cast<int>(UserClassifier::Event::kMaxValue) + 1 &&
-                  base::size(kLastTimeKeys) ==
-                      static_cast<int>(UserClassifier::Event::kMaxValue) + 1 &&
-                  base::size(kInitialHoursBetweenEvents) ==
-                      static_cast<int>(UserClassifier::Event::kMaxValue) + 1 &&
-                  base::size(kInitialHoursBetweenEventsParams) ==
-                      static_cast<int>(UserClassifier::Event::kMaxValue) + 1,
-              "Fill in info for all event types.");
-
-// Computes the discount rate.
-double GetDiscountRatePerHour() {
-  double discount_rate_per_day = variations::GetVariationParamByFeatureAsDouble(
-      kInterestFeedContentSuggestions, kDiscountRatePerDayParam,
-      kDiscountRatePerDay);
-  // Check for illegal values.
-  if (discount_rate_per_day <= 0 || discount_rate_per_day >= 1) {
-    DLOG(WARNING) << "Illegal value " << discount_rate_per_day
-                  << " for the parameter " << kDiscountRatePerDayParam
-                  << " (must be strictly between 0 and 1; the default "
-                  << kDiscountRatePerDay << " is used, instead).";
-    discount_rate_per_day = kDiscountRatePerDay;
-  }
-  // Compute discount_rate_per_hour such that
-  //   discount_rate_per_day = 1 - e^{-discount_rate_per_hour * 24}.
-  return std::log(1.0 / (1.0 - discount_rate_per_day)) / 24.0;
-}
+                  static_cast<int>(UserClassifier::Event::kMaxValue) + 1,
+              "kEvents should have all enum values.");
 
-double GetInitialHoursBetweenEvents(UserClassifier::Event event) {
-  return variations::GetVariationParamByFeatureAsDouble(
-      kInterestFeedContentSuggestions,
-      kInitialHoursBetweenEventsParams[static_cast<int>(event)],
-      kInitialHoursBetweenEvents[static_cast<int>(event)]);
+const char* GetRateKey(UserClassifier::Event event) {
+  switch (event) {
+    case UserClassifier::Event::kSuggestionsViewed:
+      return prefs::kUserClassifierAverageSuggestionsViwedPerHour;
+    case UserClassifier::Event::kSuggestionsUsed:
+      return prefs::kUserClassifierAverageSuggestionsUsedPerHour;
+  }
 }
 
-double GetMinHours() {
-  return variations::GetVariationParamByFeatureAsDouble(
-      kInterestFeedContentSuggestions, kMinHoursParam, kMinHours);
+const char* GetLastTimeKey(UserClassifier::Event event) {
+  switch (event) {
+    case UserClassifier::Event::kSuggestionsViewed:
+      return prefs::kUserClassifierLastTimeToViewSuggestions;
+    case UserClassifier::Event::kSuggestionsUsed:
+      return prefs::kUserClassifierLastTimeToUseSuggestions;
+  }
 }
 
-double GetMaxHours() {
-  return variations::GetVariationParamByFeatureAsDouble(
-      kInterestFeedContentSuggestions, kMaxHoursParam, kMaxHours);
+double GetInitialHoursBetweenEvents(UserClassifier::Event event) {
+  switch (event) {
+    case UserClassifier::Event::kSuggestionsViewed:
+      return 24;
+    case UserClassifier::Event::kSuggestionsUsed:
+      return 120;
+  }
 }
 
 // Returns the new value of the rate using its |old_value|, assuming
@@ -177,22 +141,9 @@ double GetRateForEstimateHoursBetweenEvents(double estimate_hours,
 
 }  // namespace
 
-UserClassifier::UserClassifier(PrefService* pref_service, base::Clock* clock)
-    : pref_service_(pref_service),
-      clock_(clock),
-      discount_rate_per_hour_(GetDiscountRatePerHour()),
-      min_hours_(GetMinHours()),
-      max_hours_(GetMaxHours()),
-      active_consumer_clicks_at_least_once_per_hours_(
-          variations::GetVariationParamByFeatureAsDouble(
-              kInterestFeedContentSuggestions,
-              kActiveConsumerClicksAtLeastOncePerHoursParam,
-              kActiveConsumerClicksAtLeastOncePerHours)),
-      rare_viewer_opens_surface_at_most_once_per_hours_(
-          variations::GetVariationParamByFeatureAsDouble(
-              kInterestFeedContentSuggestions,
-              kRareUserViewsAtMostOncePerHoursParam,
-              kRareUserViewsAtMostOncePerHours)) {
+UserClassifier::UserClassifier(PrefService* pref_service,
+                               const base::Clock* clock)
+    : pref_service_(pref_service), clock_(clock) {
   // The pref_service_ can be null in tests.
   if (!pref_service_) {
     return;
@@ -214,25 +165,19 @@ UserClassifier::~UserClassifier() = default;
 
 // static
 void UserClassifier::RegisterProfilePrefs(PrefRegistrySimple* registry) {
-  double discount_rate = GetDiscountRatePerHour();
-  double min_hours = GetMinHours();
-  double max_hours = GetMaxHours();
-
   for (Event event : kEvents) {
     double default_rate = GetRateForEstimateHoursBetweenEvents(
-        GetInitialHoursBetweenEvents(event), discount_rate, min_hours,
-        max_hours);
-    registry->RegisterDoublePref(kRateKeys[static_cast<int>(event)],
-                                 default_rate);
-    registry->RegisterTimePref(kLastTimeKeys[static_cast<int>(event)],
-                               base::Time());
+        GetInitialHoursBetweenEvents(event), kDiscountRatePerHour, kMinHours,
+        kMaxHours);
+    registry->RegisterDoublePref(GetRateKey(event), default_rate);
+    registry->RegisterTimePref(GetLastTimeKey(event), base::Time());
   }
 }
 
 void UserClassifier::OnEvent(Event event) {
   double metric_value = UpdateRateOnEvent(event);
-  double avg = GetEstimateHoursBetweenEvents(
-      metric_value, discount_rate_per_hour_, min_hours_, max_hours_);
+  double avg = GetEstimateHoursBetweenEvents(metric_value, kDiscountRatePerHour,
+                                             kMinHours, kMaxHours);
   // We use kMaxHours as the max value below as the maximum value for the
   // histograms must be constant.
   switch (event) {
@@ -249,23 +194,23 @@ void UserClassifier::OnEvent(Event event) {
 
 double UserClassifier::GetEstimatedAvgTime(Event event) const {
   double rate = GetUpToDateRate(event);
-  return GetEstimateHoursBetweenEvents(rate, discount_rate_per_hour_,
-                                       min_hours_, max_hours_);
+  return GetEstimateHoursBetweenEvents(rate, kDiscountRatePerHour, kMinHours,
+                                       kMaxHours);
 }
 
-UserClassifier::UserClass UserClassifier::GetUserClass() const {
+UserClass UserClassifier::GetUserClass() const {
   // The pref_service_ can be null in tests.
   if (!pref_service_) {
     return UserClass::kActiveSuggestionsViewer;
   }
 
   if (GetEstimatedAvgTime(Event::kSuggestionsViewed) >=
-      rare_viewer_opens_surface_at_most_once_per_hours_) {
+      kRareUserViewsAtMostOncePerHours) {
     return UserClass::kRareSuggestionsViewer;
   }
 
   if (GetEstimatedAvgTime(Event::kSuggestionsUsed) <=
-      active_consumer_clicks_at_least_once_per_hours_) {
+      kActiveConsumerClicksAtLeastOncePerHours) {
     return UserClass::kActiveSuggestionsConsumer;
   }
 
@@ -304,9 +249,9 @@ double UserClassifier::UpdateRateOnEvent(Event event) {
   }
 
   double hours_since_last_time =
-      std::min(max_hours_, GetHoursSinceLastTime(event));
+      std::min(kMaxHours, GetHoursSinceLastTime(event));
   // Ignore events within the same "browsing session".
-  if (hours_since_last_time < min_hours_) {
+  if (hours_since_last_time < kMinHours) {
     return GetUpToDateRate(event);
   }
 
@@ -315,7 +260,7 @@ double UserClassifier::UpdateRateOnEvent(Event event) {
   double rate = GetRate(event);
   // Add 1 to the discounted rate as the event has happened right now.
   double new_rate =
-      1 + DiscountRate(rate, hours_since_last_time, discount_rate_per_hour_);
+      1 + DiscountRate(rate, hours_since_last_time, kDiscountRatePerHour);
   SetRate(event, new_rate);
   return new_rate;
 }
@@ -326,11 +271,11 @@ double UserClassifier::GetUpToDateRate(Event event) const {
     return 0;
   }
 
-  double hours_since_last_time =
-      std::min(max_hours_, GetHoursSinceLastTime(event));
+  const double hours_since_last_time =
+      std::min(kMaxHours, GetHoursSinceLastTime(event));
 
-  double rate = GetRate(event);
-  return DiscountRate(rate, hours_since_last_time, discount_rate_per_hour_);
+  const double rate = GetRate(event);
+  return DiscountRate(rate, hours_since_last_time, kDiscountRatePerHour);
 }
 
 double UserClassifier::GetHoursSinceLastTime(Event event) const {
@@ -339,29 +284,28 @@ double UserClassifier::GetHoursSinceLastTime(Event event) const {
   }
 
   base::TimeDelta since_last_time =
-      clock_->Now() -
-      pref_service_->GetTime(kLastTimeKeys[static_cast<int>(event)]);
+      clock_->Now() - pref_service_->GetTime(GetLastTimeKey(event));
   return since_last_time.InSecondsF() / 3600;
 }
 
 bool UserClassifier::HasLastTime(Event event) const {
-  return pref_service_->HasPrefPath(kLastTimeKeys[static_cast<int>(event)]);
+  return pref_service_->HasPrefPath(GetLastTimeKey(event));
 }
 
 void UserClassifier::SetLastTimeToNow(Event event) {
-  pref_service_->SetTime(kLastTimeKeys[static_cast<int>(event)], clock_->Now());
+  pref_service_->SetTime(GetLastTimeKey(event), clock_->Now());
 }
 
 double UserClassifier::GetRate(Event event) const {
-  return pref_service_->GetDouble(kRateKeys[static_cast<int>(event)]);
+  return pref_service_->GetDouble(GetRateKey(event));
 }
 
 void UserClassifier::SetRate(Event event, double rate) {
-  pref_service_->SetDouble(kRateKeys[static_cast<int>(event)], rate);
+  pref_service_->SetDouble(GetRateKey(event), rate);
 }
 
 void UserClassifier::ClearRate(Event event) {
-  pref_service_->ClearPref(kRateKeys[static_cast<int>(event)]);
+  pref_service_->ClearPref(GetRateKey(event));
 }
 
 }  // namespace feed
diff --git a/chromium/components/feed/core/user_classifier.h b/chromium/components/feed/core/common/user_classifier.h
index e1c1ed3e1e7..154df8b88d9 100644
--- a/chromium/components/feed/core/user_classifier.h
+++ b/chromium/components/feed/core/common/user_classifier.h
@@ -2,13 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_FEED_CORE_USER_CLASSIFIER_H_
-#define COMPONENTS_FEED_CORE_USER_CLASSIFIER_H_
+#ifndef COMPONENTS_FEED_CORE_COMMON_USER_CLASSIFIER_H_
+#define COMPONENTS_FEED_CORE_COMMON_USER_CLASSIFIER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
+#include "components/feed/core/common/enums.h"
 
 class PrefRegistrySimple;
 class PrefService;
@@ -24,16 +25,6 @@ namespace feed {
 // Based on these long-term user rates, it classifies the user in a UserClass.
 class UserClassifier {
  public:
-  // Different groupings of usage. A user will belong to exactly one of these at
-  // any given point in time. Can change at runtime.
-  enum class UserClass {
-    kRareSuggestionsViewer,      // Almost never opens surfaces that show
-                                 // suggestions, like the NTP.
-    kActiveSuggestionsViewer,    // Frequently shown suggestions, but does not
-                                 // usually open them.
-    kActiveSuggestionsConsumer,  // Frequently opens news articles.
-  };
-
   // For estimating the average length of the intervals between two successive
   // events, we keep a simple frequency model, a single value that we call
   // "rate" below.
@@ -55,8 +46,8 @@ class UserClassifier {
   };
 
   // The provided |pref_service| may be nullptr in unit-tests.
-  UserClassifier(PrefService* pref_service, base::Clock* clock);
-  ~UserClassifier();
+  UserClassifier(PrefService* pref_service, const base::Clock* clock);
+  virtual ~UserClassifier();
 
   // Registers profile prefs for all rates. Called from pref_names.cc.
   static void RegisterProfilePrefs(PrefRegistrySimple* registry);
@@ -70,7 +61,8 @@ class UserClassifier {
   double GetEstimatedAvgTime(Event event) const;
 
   // Return the classification of the current user.
-  UserClass GetUserClass() const;
+  // Virtual for testing.
+  virtual UserClass GetUserClass() const;
   std::string GetUserClassDescriptionForDebugging() const;
 
   // Resets the classification (emulates a fresh upgrade / install).
@@ -95,20 +87,11 @@ class UserClassifier {
   void ClearRate(Event event);
 
   PrefService* pref_service_;
-  base::Clock* clock_;
-
-  // Params of the rate.
-  const double discount_rate_per_hour_;
-  const double min_hours_;
-  const double max_hours_;
-
-  // Params of the classification.
-  const double active_consumer_clicks_at_least_once_per_hours_;
-  const double rare_viewer_opens_surface_at_most_once_per_hours_;
+  const base::Clock* clock_;
 
   DISALLOW_COPY_AND_ASSIGN(UserClassifier);
 };
 
 }  // namespace feed
 
-#endif  // COMPONENTS_FEED_CORE_USER_CLASSIFIER_H_
+#endif  // COMPONENTS_FEED_CORE_COMMON_USER_CLASSIFIER_H_
diff --git a/chromium/components/feed/core/user_classifier_unittest.cc b/chromium/components/feed/core/common/user_classifier_unittest.cc
index 84aa9a6cb59..6d0eebb0eee 100644
--- a/chromium/components/feed/core/user_classifier_unittest.cc
+++ b/chromium/components/feed/core/common/user_classifier_unittest.cc
@@ -2,17 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/user_classifier.h"
 
 #include <memory>
 #include <string>
 #include <utility>
 
 #include "base/test/metrics/histogram_tester.h"
-#include "base/test/scoped_feature_list.h"
 #include "base/test/simple_test_clock.h"
 #include "base/time/time.h"
-#include "components/feed/feed_feature_list.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/testing_pref_service.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ -59,7 +57,7 @@ class FeedUserClassifierTest : public testing::Test {
 TEST_F(FeedUserClassifierTest, ShouldBeActiveSuggestionsViewerInitially) {
   UserClassifier* user_classifier = CreateUserClassifier();
   EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsViewer));
+              Eq(UserClass::kActiveSuggestionsViewer));
 }
 
 TEST_F(FeedUserClassifierTest,
@@ -69,7 +67,7 @@ TEST_F(FeedUserClassifierTest,
   // After one click still only an active user.
   user_classifier->OnEvent(UserClassifier::Event::kSuggestionsUsed);
   EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsViewer));
+              Eq(UserClass::kActiveSuggestionsViewer));
 
   // After a few more clicks, become an active consumer.
   for (int i = 0; i < 5; i++) {
@@ -77,31 +75,7 @@ TEST_F(FeedUserClassifierTest,
     user_classifier->OnEvent(UserClassifier::Event::kSuggestionsUsed);
   }
   EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsConsumer));
-}
-
-TEST_F(FeedUserClassifierTest,
-       ShouldBecomeActiveSuggestionsConsumerByClickingOftenWithDecreasedParam) {
-  // Increase the param to one half.
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeatureWithParameters(
-      kInterestFeedContentSuggestions,
-      {{"user_classifier_active_consumer_clicks_at_least_once_per_hours",
-        "36"}});
-  UserClassifier* user_classifier = CreateUserClassifier();
-
-  // After two clicks still only an active user.
-  user_classifier->OnEvent(UserClassifier::Event::kSuggestionsUsed);
-  test_clock()->Advance(base::TimeDelta::FromHours(1));
-  user_classifier->OnEvent(UserClassifier::Event::kSuggestionsUsed);
-  EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsViewer));
-
-  // One more click to become an active consumer.
-  test_clock()->Advance(base::TimeDelta::FromHours(1));
-  user_classifier->OnEvent(UserClassifier::Event::kSuggestionsUsed);
-  EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsConsumer));
+              Eq(UserClass::kActiveSuggestionsConsumer));
 }
 
 TEST_F(FeedUserClassifierTest,
@@ -111,32 +85,12 @@ TEST_F(FeedUserClassifierTest,
   // After two days of waiting still an active user.
   test_clock()->Advance(base::TimeDelta::FromDays(2));
   EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsViewer));
+              Eq(UserClass::kActiveSuggestionsViewer));
 
   // Two more days to become a rare user.
   test_clock()->Advance(base::TimeDelta::FromDays(2));
   EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kRareSuggestionsViewer));
-}
-
-TEST_F(FeedUserClassifierTest,
-       ShouldBecomeRareSuggestionsViewerByNoActivityWithDecreasedParam) {
-  // Decrease the param to one half.
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeatureWithParameters(
-      kInterestFeedContentSuggestions,
-      {{"user_classifier_rare_user_views_at_most_once_per_hours", "48"}});
-  UserClassifier* user_classifier = CreateUserClassifier();
-
-  // After one days of waiting still an active user.
-  test_clock()->Advance(base::TimeDelta::FromDays(1));
-  EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kActiveSuggestionsViewer));
-
-  // One more day to become a rare user.
-  test_clock()->Advance(base::TimeDelta::FromDays(1));
-  EXPECT_THAT(user_classifier->GetUserClass(),
-              Eq(UserClassifier::UserClass::kRareSuggestionsViewer));
+              Eq(UserClass::kRareSuggestionsViewer));
 }
 
 class FeedUserClassifierEventTest
@@ -220,31 +174,6 @@ TEST_P(FeedUserClassifierEventTest, ShouldIgnoreSubsequentEventsForHalfAnHour) {
   EXPECT_THAT(user_classifier->GetEstimatedAvgTime(event), Lt(old_rate));
 }
 
-TEST_P(FeedUserClassifierEventTest,
-       ShouldIgnoreSubsequentEventsWithIncreasedLimit) {
-  UserClassifier::Event event = GetParam().first;
-  // Increase the min_hours to 1.0, i.e. 60 minutes.
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeatureWithParameters(
-      kInterestFeedContentSuggestions, {{"user_classifier_min_hours", "1.0"}});
-  UserClassifier* user_classifier = CreateUserClassifier();
-
-  // The initial event.
-  user_classifier->OnEvent(event);
-  // Subsequent events get ignored for the next 60 minutes.
-  for (int i = 0; i < 11; i++) {
-    test_clock()->Advance(base::TimeDelta::FromMinutes(5));
-    double old_rate = user_classifier->GetEstimatedAvgTime(event);
-    user_classifier->OnEvent(event);
-    EXPECT_THAT(user_classifier->GetEstimatedAvgTime(event), Eq(old_rate));
-  }
-  // An event 60 minutes after the initial event is finally not ignored.
-  test_clock()->Advance(base::TimeDelta::FromMinutes(5));
-  double old_rate = user_classifier->GetEstimatedAvgTime(event);
-  user_classifier->OnEvent(event);
-  EXPECT_THAT(user_classifier->GetEstimatedAvgTime(event), Lt(old_rate));
-}
-
 TEST_P(FeedUserClassifierEventTest, ShouldCapDelayBetweenEvents) {
   UserClassifier::Event event = GetParam().first;
   UserClassifier* user_classifier = CreateUserClassifier();
@@ -267,33 +196,6 @@ TEST_P(FeedUserClassifierEventTest, ShouldCapDelayBetweenEvents) {
               Eq(rate_after_a_year));
 }
 
-TEST_P(FeedUserClassifierEventTest,
-       ShouldCapDelayBetweenEventsWithDecreasedLimit) {
-  UserClassifier::Event event = GetParam().first;
-  // Decrease the max_hours to 72, i.e. 3 days.
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitAndEnableFeatureWithParameters(
-      kInterestFeedContentSuggestions, {{"user_classifier_max_hours", "72"}});
-  UserClassifier* user_classifier = CreateUserClassifier();
-
-  // The initial event.
-  user_classifier->OnEvent(event);
-  // Wait for an insane amount of time
-  test_clock()->Advance(base::TimeDelta::FromDays(365));
-  user_classifier->OnEvent(event);
-  double rate_after_a_year = user_classifier->GetEstimatedAvgTime(event);
-
-  // Now repeat the same with s/one year/two days.
-  user_classifier->ClearClassificationForDebugging();
-  user_classifier->OnEvent(event);
-  test_clock()->Advance(base::TimeDelta::FromDays(3));
-  user_classifier->OnEvent(event);
-
-  // The results should be the same.
-  EXPECT_THAT(user_classifier->GetEstimatedAvgTime(event),
-              Eq(rate_after_a_year));
-}
-
 INSTANTIATE_TEST_SUITE_P(
     All,  // An empty prefix for the parametrized tests names (no need to
           // distinguish the only instance we make here).
diff --git a/chromium/components/feed/core/feed_content_database.cc b/chromium/components/feed/core/feed_content_database.cc
index 4ea33bd29b1..df1d0588a9f 100644
--- a/chromium/components/feed/core/feed_content_database.cc
+++ b/chromium/components/feed/core/feed_content_database.cc
@@ -12,6 +12,7 @@
 #include "base/strings/string_util.h"
 #include "base/system/sys_info.h"
 #include "base/task/post_task.h"
+#include "base/task/thread_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/feed/core/feed_content_mutation.h"
 #include "components/feed/core/feed_content_operation.h"
@@ -53,9 +54,8 @@ FeedContentDatabase::FeedContentDatabase(
     leveldb_proto::ProtoDatabaseProvider* proto_database_provider,
     const base::FilePath& database_folder)
     : database_status_(InitStatus::kNotInitialized),
-      task_runner_(
-          base::CreateSequencedTaskRunner({base::ThreadPool(), base::MayBlock(),
-                                           base::TaskPriority::USER_VISIBLE})),
+      task_runner_(base::ThreadPool::CreateSequencedTaskRunner(
+          {base::MayBlock(), base::TaskPriority::USER_VISIBLE})),
       storage_database_(proto_database_provider->GetDB<ContentStorageProto>(
           leveldb_proto::ProtoDbType::FEED_CONTENT_DATABASE,
           database_folder.AppendASCII(kContentDatabaseFolder),
diff --git a/chromium/components/feed/core/feed_content_database_unittest.cc b/chromium/components/feed/core/feed_content_database_unittest.cc
index d455fe6e270..ab9e3431c77 100644
--- a/chromium/components/feed/core/feed_content_database_unittest.cc
+++ b/chromium/components/feed/core/feed_content_database_unittest.cc
@@ -7,6 +7,7 @@
 #include <map>
 
 #include "base/bind.h"
+#include "base/task/thread_pool.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/task_environment.h"
 #include "components/feed/core/feed_content_mutation.h"
@@ -57,9 +58,8 @@ class FeedContentDatabaseTest : public testing::Test {
     auto storage_db =
         std::make_unique<FakeDB<ContentStorageProto>>(&content_db_storage_);
 
-    task_runner_ =
-        base::CreateSequencedTaskRunner({base::ThreadPool(), base::MayBlock(),
-                                         base::TaskPriority::USER_VISIBLE});
+    task_runner_ = base::ThreadPool::CreateSequencedTaskRunner(
+        {base::MayBlock(), base::TaskPriority::USER_VISIBLE});
 
     content_db_ = storage_db.get();
     feed_db_ = std::make_unique<FeedContentDatabase>(std::move(storage_db),
diff --git a/chromium/components/feed/core/feed_journal_database.cc b/chromium/components/feed/core/feed_journal_database.cc
index 64539b6d404..63a4540af73 100644
--- a/chromium/components/feed/core/feed_journal_database.cc
+++ b/chromium/components/feed/core/feed_journal_database.cc
@@ -10,6 +10,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/system/sys_info.h"
 #include "base/task/post_task.h"
+#include "base/task/thread_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/feed/core/feed_journal_mutation.h"
 #include "components/feed/core/feed_journal_operation.h"
@@ -38,9 +39,8 @@ FeedJournalDatabase::FeedJournalDatabase(
     leveldb_proto::ProtoDatabaseProvider* proto_database_provider,
     const base::FilePath& database_folder)
     : database_status_(InitStatus::kNotInitialized),
-      task_runner_(
-          base::CreateSequencedTaskRunner({base::ThreadPool(), base::MayBlock(),
-                                           base::TaskPriority::USER_VISIBLE})),
+      task_runner_(base::ThreadPool::CreateSequencedTaskRunner(
+          {base::MayBlock(), base::TaskPriority::USER_VISIBLE})),
       storage_database_(proto_database_provider->GetDB<JournalStorageProto>(
           leveldb_proto::ProtoDbType::FEED_JOURNAL_DATABASE,
           database_folder.AppendASCII(kJournalDatabaseFolder),
diff --git a/chromium/components/feed/core/feed_journal_database_unittest.cc b/chromium/components/feed/core/feed_journal_database_unittest.cc
index 6f2a238835c..cd0b2debc01 100644
--- a/chromium/components/feed/core/feed_journal_database_unittest.cc
+++ b/chromium/components/feed/core/feed_journal_database_unittest.cc
@@ -8,6 +8,7 @@
 #include <utility>
 
 #include "base/bind.h"
+#include "base/task/thread_pool.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/task_environment.h"
 #include "components/feed/core/feed_journal_mutation.h"
@@ -63,9 +64,8 @@ class FeedJournalDatabaseTest : public testing::Test {
     auto storage_db =
         std::make_unique<FakeDB<JournalStorageProto>>(&journal_db_storage_);
 
-    task_runner_ =
-        base::CreateSequencedTaskRunner({base::ThreadPool(), base::MayBlock(),
-                                         base::TaskPriority::USER_VISIBLE});
+    task_runner_ = base::ThreadPool::CreateSequencedTaskRunner(
+        {base::MayBlock(), base::TaskPriority::USER_VISIBLE});
 
     journal_db_ = storage_db.get();
     feed_db_ = std::make_unique<FeedJournalDatabase>(std::move(storage_db),
diff --git a/chromium/components/feed/core/feed_logging_metrics_unittest.cc b/chromium/components/feed/core/feed_logging_metrics_unittest.cc
index 100a458def0..3463ccc3d13 100644
--- a/chromium/components/feed/core/feed_logging_metrics_unittest.cc
+++ b/chromium/components/feed/core/feed_logging_metrics_unittest.cc
@@ -8,8 +8,8 @@
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/simple_test_clock.h"
 #include "base/time/time.h"
-#include "components/feed/core/pref_names.h"
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/common/user_classifier.h"
 #include "components/prefs/testing_pref_service.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -22,8 +22,6 @@ using testing::SizeIs;
 namespace feed {
 namespace {
 
-GURL kVisitedUrl("http://visited_url.com/");
-
 // Fixed "now" to make tests more deterministic.
 char kNowString[] = "2018-06-11 15:41";
 
@@ -39,9 +37,15 @@ enum FeedActionType {
   DOWNLOAD = 5,
 };
 
+// TODO(https://crbug.com/1042727): Fix test GURL scoping and remove this getter
+// function.
+GURL VisitedUrl() {
+  return GURL("http://visited_url.com/");
+}
+
 void CheckURLVisit(const GURL& url,
                    FeedLoggingMetrics::CheckURLVisitCallback callback) {
-  if (url == kVisitedUrl) {
+  if (url == VisitedUrl()) {
     std::move(callback).Run(true);
   } else {
     std::move(callback).Run(false);
@@ -178,7 +182,7 @@ TEST_F(FeedLoggingMetricsTest, ShouldLogOnSuggestionWindowOpened) {
 
 TEST_F(FeedLoggingMetricsTest, ShouldLogOnSuggestionDismissedCommitIfVisited) {
   base::HistogramTester histogram_tester;
-  feed_logging_metrics()->OnSuggestionDismissed(/*position=*/10, kVisitedUrl,
+  feed_logging_metrics()->OnSuggestionDismissed(/*position=*/10, VisitedUrl(),
                                                 true);
   EXPECT_THAT(histogram_tester.GetAllSamples(
                   "NewTabPage.ContentSuggestions.DismissedVisited.Commit"),
@@ -198,7 +202,7 @@ TEST_F(FeedLoggingMetricsTest,
 TEST_F(FeedLoggingMetricsTest,
        ShouldLogOnSuggestionDismissedUndoIfUndoDismissAndVisited) {
   base::HistogramTester histogram_tester;
-  feed_logging_metrics()->OnSuggestionDismissed(/*position=*/10, kVisitedUrl,
+  feed_logging_metrics()->OnSuggestionDismissed(/*position=*/10, VisitedUrl(),
                                                 false);
   EXPECT_THAT(histogram_tester.GetAllSamples(
                   "NewTabPage.ContentSuggestions.DismissedVisited.Undo"),
diff --git a/chromium/components/feed/core/feed_networking_host.cc b/chromium/components/feed/core/feed_networking_host.cc
index 04c6848fac8..e6ab4ac9321 100644
--- a/chromium/components/feed/core/feed_networking_host.cc
+++ b/chromium/components/feed/core/feed_networking_host.cc
@@ -14,12 +14,13 @@
 #include "base/time/tick_clock.h"
 #include "base/time/time.h"
 #include "base/values.h"
-#include "components/feed/core/pref_names.h"
+#include "components/feed/core/common/pref_names.h"
 #include "components/feed/feed_feature_list.h"
 #include "components/prefs/pref_service.h"
 #include "components/signin/public/identity_manager/access_token_info.h"
 #include "components/signin/public/identity_manager/identity_manager.h"
 #include "components/signin/public/identity_manager/primary_account_access_token_fetcher.h"
+#include "components/signin/public/identity_manager/scope_set.h"
 #include "components/variations/net/variations_http_headers.h"
 #include "google_apis/gaia/google_service_auth_error.h"
 #include "net/base/load_flags.h"
@@ -77,7 +78,8 @@ class NetworkFetch {
                                 signin::AccessTokenInfo access_token_info);
   void StartLoader();
   std::unique_ptr<network::SimpleURLLoader> MakeLoader();
-  void SetRequestHeaders(network::ResourceRequest* request) const;
+  void SetRequestHeaders(bool has_request_body,
+                         network::ResourceRequest* request) const;
   void PopulateRequestBody(network::SimpleURLLoader* loader);
   void OnSimpleLoaderComplete(std::unique_ptr<std::string> response);
 
@@ -150,7 +152,7 @@ void NetworkFetch::Start(FeedNetworkingHost::ResponseCallback done_callback) {
 }
 
 void NetworkFetch::StartAccessTokenFetch() {
-  identity::ScopeSet scopes{kAuthenticationScope};
+  signin::ScopeSet scopes{kAuthenticationScope};
   // It's safe to pass base::Unretained(this) since deleting the token fetcher
   // will prevent the callback from being completed.
   token_fetcher_ = std::make_unique<signin::PrimaryAccountAccessTokenFetcher>(
@@ -229,10 +231,10 @@ std::unique_ptr<network::SimpleURLLoader> NetworkFetch::MakeLoader() {
   if (host_overridden_) {
     resource_request->credentials_mode =
         network::mojom::CredentialsMode::kInclude;
-    resource_request->site_for_cookies = url;
+    resource_request->site_for_cookies = net::SiteForCookies::FromUrl(url);
   }
 
-  SetRequestHeaders(resource_request.get());
+  SetRequestHeaders(!request_body_.empty(), resource_request.get());
 
   auto simple_loader = network::SimpleURLLoader::Create(
       std::move(resource_request), traffic_annotation);
@@ -243,10 +245,13 @@ std::unique_ptr<network::SimpleURLLoader> NetworkFetch::MakeLoader() {
   return simple_loader;
 }
 
-void NetworkFetch::SetRequestHeaders(network::ResourceRequest* request) const {
-  request->headers.SetHeader(net::HttpRequestHeaders::kContentType,
-                             kContentType);
-  request->headers.SetHeader(kContentEncoding, kGzip);
+void NetworkFetch::SetRequestHeaders(bool has_request_body,
+                                     network::ResourceRequest* request) const {
+  if (has_request_body) {
+    request->headers.SetHeader(net::HttpRequestHeaders::kContentType,
+                               kContentType);
+    request->headers.SetHeader(kContentEncoding, kGzip);
+  }
 
   variations::SignedIn signed_in_status = variations::SignedIn::kNo;
   if (!access_token_.empty()) {
@@ -306,7 +311,7 @@ void NetworkFetch::OnSimpleLoaderComplete(
     status_code = simple_loader_->ResponseInfo()->headers->response_code();
 
     if (status_code == net::HTTP_UNAUTHORIZED) {
-      identity::ScopeSet scopes{kAuthenticationScope};
+      signin::ScopeSet scopes{kAuthenticationScope};
       CoreAccountId account_id = identity_manager_->GetPrimaryAccountId();
       if (!account_id.empty()) {
         identity_manager_->RemoveAccessTokenFromCache(account_id, scopes,
diff --git a/chromium/components/feed/core/feed_networking_host_unittest.cc b/chromium/components/feed/core/feed_networking_host_unittest.cc
index 51901925d3d..9361ec2dd7d 100644
--- a/chromium/components/feed/core/feed_networking_host_unittest.cc
+++ b/chromium/components/feed/core/feed_networking_host_unittest.cc
@@ -14,7 +14,7 @@
 #include "base/test/scoped_feature_list.h"
 #include "base/test/simple_test_tick_clock.h"
 #include "base/test/task_environment.h"
-#include "components/feed/core/pref_names.h"
+#include "components/feed/core/common/pref_names.h"
 #include "components/feed/feed_feature_list.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/signin/public/identity_manager/identity_test_environment.h"
@@ -246,7 +246,6 @@ TEST_F(FeedNetworkingHostTest, ShouldSetHeadersCorrectly) {
   MockResponseDoneCallback done_callback;
   net::HttpRequestHeaders headers;
   base::RunLoop interceptor_run_loop;
-  base::HistogramTester histogram_tester;
 
   test_factory()->SetInterceptor(
       base::BindLambdaForTesting([&](const network::ResourceRequest& request) {
@@ -254,9 +253,9 @@ TEST_F(FeedNetworkingHostTest, ShouldSetHeadersCorrectly) {
         interceptor_run_loop.Quit();
       }));
 
-  SendRequestAndRespond("http://foobar.com/feed", "POST", "", "",
-                      net::HTTP_OK, network::URLLoaderCompletionStatus(),
-                      &done_callback);
+  SendRequestAndRespond("http://foobar.com/feed", "POST", "body", "",
+                        net::HTTP_OK, network::URLLoaderCompletionStatus(),
+                        &done_callback);
 
   std::string content_encoding;
   std::string authorization;
@@ -267,6 +266,23 @@ TEST_F(FeedNetworkingHostTest, ShouldSetHeadersCorrectly) {
   EXPECT_EQ(authorization, "Bearer access_token");
 }
 
+TEST_F(FeedNetworkingHostTest, ShouldNotSendContentEncodingForEmptyBody) {
+  MockResponseDoneCallback done_callback;
+  net::HttpRequestHeaders headers;
+  base::RunLoop interceptor_run_loop;
+
+  test_factory()->SetInterceptor(
+      base::BindLambdaForTesting([&](const network::ResourceRequest& request) {
+        headers = request.headers;
+        interceptor_run_loop.Quit();
+      }));
+
+  SendRequestAndRespond("http://foobar.com/feed", "GET", "", "", net::HTTP_OK,
+                        network::URLLoaderCompletionStatus(), &done_callback);
+
+  EXPECT_FALSE(headers.HasHeader("content-encoding"));
+}
+
 TEST_F(FeedNetworkingHostTest, ShouldReportSizeHistograms) {
   std::string uncompressed_request_string(2048, 'a');
   std::string response_string(1024, 'b');
diff --git a/chromium/components/feed/core/feed_scheduler_host.cc b/chromium/components/feed/core/feed_scheduler_host.cc
index 627cf56386b..5b492c90e98 100644
--- a/chromium/components/feed/core/feed_scheduler_host.cc
+++ b/chromium/components/feed/core/feed_scheduler_host.cc
@@ -16,7 +16,8 @@
 #include "base/strings/stringprintf.h"
 #include "base/time/clock.h"
 #include "base/time/time.h"
-#include "components/feed/core/pref_names.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/shared_prefs/pref_names.h"
 #include "components/feed/core/time_serialization.h"
 #include "components/feed/feed_feature_list.h"
 #include "components/prefs/pref_service.h"
@@ -27,9 +28,6 @@ namespace feed {
 
 namespace {
 
-using TriggerType = FeedSchedulerHost::TriggerType;
-using UserClass = UserClassifier::UserClass;
-
 // Enum for the relation between boolean fields the Feed and host both track.
 // Reported through UMA and must match the corresponding definition in
 // enums.xml
@@ -41,21 +39,16 @@ enum class FeedHostMismatch {
   kMaxValue = kBothAreSet,
 };
 
-// Copies boolean args into temps to avoid evaluating them multiple times.
-#define UMA_HISTOGRAM_MISMATCH(name, feed_is_set, host_is_set)  \
-  do {                                                          \
-    bool copied_feed_is_set = feed_is_set;                      \
-    bool copied_host_is_set = host_is_set;                      \
-    FeedHostMismatch status = FeedHostMismatch::kNeitherAreSet; \
-    if (copied_feed_is_set && copied_host_is_set) {             \
-      status = FeedHostMismatch::kBothAreSet;                   \
-    } else if (copied_feed_is_set) {                            \
-      status = FeedHostMismatch::kFeedIsSetOnly;                \
-    } else if (copied_host_is_set) {                            \
-      status = FeedHostMismatch::kHostIsSetOnly;                \
-    }                                                           \
-    UMA_HISTOGRAM_ENUMERATION(name, status);                    \
-  } while (false);
+FeedHostMismatch GetMismatch(bool feed_is_set, bool host_is_set) {
+  if (feed_is_set && host_is_set) {
+    return FeedHostMismatch::kBothAreSet;
+  } else if (feed_is_set) {
+    return FeedHostMismatch::kFeedIsSetOnly;
+  } else if (host_is_set) {
+    return FeedHostMismatch::kHostIsSetOnly;
+  }
+  return FeedHostMismatch::kNeitherAreSet;
+}
 
 struct ParamPair {
   std::string name;
@@ -136,15 +129,15 @@ void TryRun(base::OnceClosure closure) {
   }
 }
 
-// Converts UserClassifier::UserClass to a string that corresponds to the
+// Converts UserClass to a string that corresponds to the
 // entries in histogram suffix "UserClasses".
-std::string UserClassToHistogramSuffix(UserClassifier::UserClass user_class) {
+std::string UserClassToHistogramSuffix(UserClass user_class) {
   switch (user_class) {
-    case UserClassifier::UserClass::kRareSuggestionsViewer:
+    case UserClass::kRareSuggestionsViewer:
       return "RareNTPUser";
-    case UserClassifier::UserClass::kActiveSuggestionsViewer:
+    case UserClass::kActiveSuggestionsViewer:
       return "ActiveNTPUser";
-    case UserClassifier::UserClass::kActiveSuggestionsConsumer:
+    case UserClass::kActiveSuggestionsConsumer:
       return "ActiveSuggestionsConsumer";
   }
 }
@@ -155,7 +148,7 @@ std::string UserClassToHistogramSuffix(UserClassifier::UserClass user_class) {
 // because this method is only called as a result of a direct user interaction,
 // like opening the NTP or foregrounding the browser.
 void ReportAgeWithSuffix(const std::string& qualified_trigger,
-                         UserClassifier::UserClass user_class,
+                         UserClass user_class,
                          base::TimeDelta sample) {
   std::string name = base::StringPrintf(
       "NewTabPage.ContentSuggestions.%s.%s", qualified_trigger.c_str(),
@@ -165,10 +158,9 @@ void ReportAgeWithSuffix(const std::string& qualified_trigger,
                                 /*bucket_count=*/50);
 }
 
-void ReportReasonForNotRefreshingByBehavior(
-    NativeRequestBehavior behavior,
-    FeedSchedulerHost::ShouldRefreshResult status) {
-  DCHECK_NE(status, FeedSchedulerHost::kShouldRefresh);
+void ReportReasonForNotRefreshingByBehavior(NativeRequestBehavior behavior,
+                                            ShouldRefreshResult status) {
+  DCHECK_NE(status, ShouldRefreshResult::kShouldRefresh);
   switch (behavior) {
     case kNoRequestWithWait:
       UMA_HISTOGRAM_ENUMERATION(
@@ -197,24 +189,23 @@ void ReportReasonForNotRefreshingByBehavior(
   }
 }
 
-void ReportReasonForNotRefreshingByTrigger(
-    FeedSchedulerHost::TriggerType trigger_type,
-    FeedSchedulerHost::ShouldRefreshResult status) {
-  DCHECK_NE(status, FeedSchedulerHost::kShouldRefresh);
+void ReportReasonForNotRefreshingByTrigger(TriggerType trigger_type,
+                                           ShouldRefreshResult status) {
+  DCHECK_NE(status, ShouldRefreshResult::kShouldRefresh);
   switch (trigger_type) {
-    case FeedSchedulerHost::TriggerType::kNtpShown:
+    case TriggerType::kNtpShown:
       UMA_HISTOGRAM_ENUMERATION(
           "ContentSuggestions.Feed.Scheduler.ShouldRefreshResult."
           "RequestByNtpShown",
           status);
       break;
-    case FeedSchedulerHost::TriggerType::kForegrounded:
+    case TriggerType::kForegrounded:
       UMA_HISTOGRAM_ENUMERATION(
           "ContentSuggestions.Feed.Scheduler.ShouldRefreshResult."
           "RequestByForegrounded",
           status);
       break;
-    case FeedSchedulerHost::TriggerType::kFixedTimer:
+    case TriggerType::kFixedTimer:
       UMA_HISTOGRAM_ENUMERATION(
           "ContentSuggestions.Feed.Scheduler.ShouldRefreshResult."
           "RequestByFixedTimer",
@@ -240,18 +231,18 @@ FeedSchedulerHost::FeedSchedulerHost(PrefService* profile_prefs,
     eula_accepted_notifier_->Init(this);
   }
 
-  throttlers_.emplace(UserClassifier::UserClass::kRareSuggestionsViewer,
-                      std::make_unique<RefreshThrottler>(
-                          UserClassifier::UserClass::kRareSuggestionsViewer,
-                          profile_prefs_, clock_));
-  throttlers_.emplace(UserClassifier::UserClass::kActiveSuggestionsViewer,
-                      std::make_unique<RefreshThrottler>(
-                          UserClassifier::UserClass::kActiveSuggestionsViewer,
-                          profile_prefs_, clock_));
-  throttlers_.emplace(UserClassifier::UserClass::kActiveSuggestionsConsumer,
-                      std::make_unique<RefreshThrottler>(
-                          UserClassifier::UserClass::kActiveSuggestionsConsumer,
-                          profile_prefs_, clock_));
+  throttlers_.emplace(
+      UserClass::kRareSuggestionsViewer,
+      std::make_unique<RefreshThrottler>(UserClass::kRareSuggestionsViewer,
+                                         profile_prefs_, clock_));
+  throttlers_.emplace(
+      UserClass::kActiveSuggestionsViewer,
+      std::make_unique<RefreshThrottler>(UserClass::kActiveSuggestionsViewer,
+                                         profile_prefs_, clock_));
+  throttlers_.emplace(
+      UserClass::kActiveSuggestionsConsumer,
+      std::make_unique<RefreshThrottler>(UserClass::kActiveSuggestionsConsumer,
+                                         profile_prefs_, clock_));
 }
 
 FeedSchedulerHost::~FeedSchedulerHost() = default;
@@ -292,9 +283,10 @@ NativeRequestBehavior FeedSchedulerHost::ShouldSessionRequestData(
   // Both the Feed and the scheduler track if there are outstanding requests.
   // It's possible that this data gets out of sync. We treat the Feed as
   // authoritative and we change our values to match.
-  UMA_HISTOGRAM_MISMATCH("ContentSuggestions.Feed.Scheduler.OutstandingRequest",
-                         has_outstanding_request,
-                         !outstanding_request_until_.is_null());
+  UMA_HISTOGRAM_ENUMERATION(
+      "ContentSuggestions.Feed.Scheduler.OutstandingRequest",
+      GetMismatch(has_outstanding_request,
+                  !outstanding_request_until_.is_null()));
   if (has_outstanding_request == outstanding_request_until_.is_null()) {
     if (has_outstanding_request) {
       outstanding_request_until_ =
@@ -312,8 +304,9 @@ NativeRequestBehavior FeedSchedulerHost::ShouldSessionRequestData(
   bool scheduler_thinks_has_content =
       !profile_prefs_->FindPreference(prefs::kLastFetchAttemptTime)
            ->IsDefaultValue();
-  UMA_HISTOGRAM_MISMATCH("ContentSuggestions.Feed.Scheduler.HasContent",
-                         has_content, scheduler_thinks_has_content);
+  UMA_HISTOGRAM_ENUMERATION(
+      "ContentSuggestions.Feed.Scheduler.HasContent",
+      GetMismatch(has_content, scheduler_thinks_has_content));
   if (has_content != scheduler_thinks_has_content) {
     if (has_content) {
       profile_prefs_->SetTime(prefs::kLastFetchAttemptTime,
@@ -342,7 +335,7 @@ NativeRequestBehavior FeedSchedulerHost::ShouldSessionRequestData(
 
   NativeRequestBehavior behavior;
   ShouldRefreshResult refresh_status = ShouldRefresh(TriggerType::kNtpShown);
-  if (kShouldRefresh == refresh_status) {
+  if (ShouldRefreshResult::kShouldRefresh == refresh_status) {
     if (!has_content) {
       behavior = kRequestWithWait;
     } else if (IsContentStale(content_creation_date_time)) {
@@ -406,7 +399,7 @@ void FeedSchedulerHost::OnForegrounded() {
   DCHECK(refresh_callback_);
   ShouldRefreshResult refresh_status =
       ShouldRefresh(TriggerType::kForegrounded);
-  if (kShouldRefresh == refresh_status) {
+  if (ShouldRefreshResult::kShouldRefresh == refresh_status) {
     refresh_callback_.Run();
   } else {
     ReportReasonForNotRefreshingByTrigger(TriggerType::kForegrounded,
@@ -426,7 +419,7 @@ void FeedSchedulerHost::OnFixedTimer(base::OnceClosure on_completion) {
   }
 
   ShouldRefreshResult refresh_status = ShouldRefresh(TriggerType::kFixedTimer);
-  if (kShouldRefresh == refresh_status) {
+  if (ShouldRefreshResult::kShouldRefresh == refresh_status) {
     // There shouldn't typically be anything in |fixed_timer_completion_| right
     // now, but if there was, run it before we replace it.
     TryRun(std::move(fixed_timer_completion_));
@@ -476,7 +469,7 @@ bool FeedSchedulerHost::OnArticlesCleared(bool suppress_refreshes) {
   }
 
   ShouldRefreshResult refresh_status = ShouldRefresh(TriggerType::kNtpShown);
-  if (kShouldRefresh == refresh_status) {
+  if (ShouldRefreshResult::kShouldRefresh == refresh_status) {
     // Instead of using |refresh_callback_|, instead return our desire to
     // refresh back up to our caller. This allows more information to be given
     // all at once to the Feed which allows it to act more intelligently.
@@ -509,41 +502,40 @@ void FeedSchedulerHost::OnEulaAccepted() {
   OnForegrounded();
 }
 
-FeedSchedulerHost::ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(
-    TriggerType trigger) {
+ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(TriggerType trigger) {
   if (clock_->Now() < outstanding_request_until_) {
     DVLOG(2) << "Outstanding request stopped refresh from trigger "
              << static_cast<int>(trigger);
-    return kDontRefreshOutstandingRequest;
+    return ShouldRefreshResult::kDontRefreshOutstandingRequest;
   }
 
   if (base::Contains(disabled_triggers_, trigger)) {
     DVLOG(2) << "Disabled trigger stopped refresh from trigger "
              << static_cast<int>(trigger);
-    return kDontRefreshTriggerDisabled;
+    return ShouldRefreshResult::kDontRefreshTriggerDisabled;
   }
 
   if (net::NetworkChangeNotifier::IsOffline()) {
     DVLOG(2) << "Network is offline stopped refresh from trigger "
              << static_cast<int>(trigger);
-    return kDontRefreshNetworkOffline;
+    return ShouldRefreshResult::kDontRefreshNetworkOffline;
   }
 
   if (eula_accepted_notifier_ && !eula_accepted_notifier_->IsEulaAccepted()) {
     DVLOG(2) << "EULA not being accepted stopped refresh from trigger "
              << static_cast<int>(trigger);
-    return kDontRefreshEulaNotAccepted;
+    return ShouldRefreshResult::kDontRefreshEulaNotAccepted;
   }
 
   if (!profile_prefs_->GetBoolean(prefs::kArticlesListVisible)) {
     DVLOG(2) << "Articles being hidden stopped refresh from trigger "
              << static_cast<int>(trigger);
-    return kDontRefreshArticlesHidden;
+    return ShouldRefreshResult::kDontRefreshArticlesHidden;
   }
 
   base::TimeDelta attempt_age =
       clock_->Now() - profile_prefs_->GetTime(prefs::kLastFetchAttemptTime);
-  UserClassifier::UserClass user_class = user_classifier_.GetUserClass();
+  UserClass user_class = user_classifier_.GetUserClass();
   if (trigger == TriggerType::kNtpShown &&
       !time_until_first_shown_trigger_reported_) {
     time_until_first_shown_trigger_reported_ = true;
@@ -560,7 +552,7 @@ FeedSchedulerHost::ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(
   if (clock_->Now() < suppress_refreshes_until_) {
     DVLOG(2) << "Refresh suppression until " << suppress_refreshes_until_
              << " stopped refresh from trigger " << static_cast<int>(trigger);
-    return kDontRefreshRefreshSuppressed;
+    return ShouldRefreshResult::kDontRefreshRefreshSuppressed;
   }
 
   // https://crbug.com/988165: When kThrottleBackgroundFetches == false, skip
@@ -569,7 +561,7 @@ FeedSchedulerHost::ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(
     if (attempt_age < GetTriggerThreshold(trigger)) {
       DVLOG(2) << "Last attempt age of " << attempt_age
                << " stopped refresh from trigger " << static_cast<int>(trigger);
-      return kDontRefreshNotStale;
+      return ShouldRefreshResult::kDontRefreshNotStale;
     }
 
     auto throttlerIter = throttlers_.find(user_class);
@@ -577,7 +569,7 @@ FeedSchedulerHost::ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(
         !throttlerIter->second->RequestQuota()) {
       DVLOG(2) << "Throttler stopped refresh from trigger "
                << static_cast<int>(trigger);
-      return kDontRefreshRefreshThrottled;
+      return ShouldRefreshResult::kDontRefreshRefreshThrottled;
     }
   }
 
@@ -602,7 +594,7 @@ FeedSchedulerHost::ShouldRefreshResult FeedSchedulerHost::ShouldRefresh(
 
   last_fetch_trigger_type_ = std::make_unique<TriggerType>(trigger);
 
-  return kShouldRefresh;
+  return ShouldRefreshResult::kShouldRefresh;
 }
 
 bool FeedSchedulerHost::IsContentStale(base::Time content_creation_date_time) {
diff --git a/chromium/components/feed/core/feed_scheduler_host.h b/chromium/components/feed/core/feed_scheduler_host.h
index 9df2d204d9e..e1e137586ec 100644
--- a/chromium/components/feed/core/feed_scheduler_host.h
+++ b/chromium/components/feed/core/feed_scheduler_host.h
@@ -13,8 +13,9 @@
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
-#include "components/feed/core/refresh_throttler.h"
-#include "components/feed/core/user_classifier.h"
+#include "components/feed/core/common/enums.h"
+#include "components/feed/core/common/refresh_throttler.h"
+#include "components/feed/core/common/user_classifier.h"
 #include "components/web_resource/eula_accepted_notifier.h"
 
 class PrefService;
@@ -49,33 +50,6 @@ enum NativeRequestBehavior {
 // content.
 class FeedSchedulerHost : web_resource::EulaAcceptedNotifier::Observer {
  public:
-  // The TriggerType enum specifies values for the events that can trigger
-  // refreshing articles. When adding values, be certain to also update the
-  // corresponding definition in enums.xml.
-  enum class TriggerType {
-    kNtpShown = 0,
-    kForegrounded = 1,
-    kFixedTimer = 2,
-    kMaxValue = kFixedTimer
-  };
-
-  // Enum for the status of the refresh, reported through UMA.
-  // If any new values are added, update the corresponding definition in
-  // enums.xml.
-  // These values are persisted to logs. Entries should not be renumbered and
-  // numeric values should never be reused.
-  enum ShouldRefreshResult {
-    kShouldRefresh = 0,
-    kDontRefreshOutstandingRequest = 1,
-    kDontRefreshTriggerDisabled = 2,
-    kDontRefreshNetworkOffline = 3,
-    kDontRefreshEulaNotAccepted = 4,
-    kDontRefreshArticlesHidden = 5,
-    kDontRefreshRefreshSuppressed = 6,
-    kDontRefreshNotStale = 7,
-    kDontRefreshRefreshThrottled = 8,
-    kMaxValue = kDontRefreshRefreshThrottled,
-  };
 
   FeedSchedulerHost(PrefService* profile_prefs,
                     PrefService* local_state,
@@ -224,8 +198,7 @@ class FeedSchedulerHost : web_resource::EulaAcceptedNotifier::Observer {
 
   // In the case the user transitions between user classes, hold onto a
   // throttler for any situation.
-  base::flat_map<UserClassifier::UserClass, std::unique_ptr<RefreshThrottler>>
-      throttlers_;
+  base::flat_map<UserClass, std::unique_ptr<RefreshThrottler>> throttlers_;
 
   // Status of the last fetch for debugging.
   int last_fetch_status_ = 0;
diff --git a/chromium/components/feed/core/feed_scheduler_host_unittest.cc b/chromium/components/feed/core/feed_scheduler_host_unittest.cc
index e0f1e40dbc6..33dfcf9aec6 100644
--- a/chromium/components/feed/core/feed_scheduler_host_unittest.cc
+++ b/chromium/components/feed/core/feed_scheduler_host_unittest.cc
@@ -13,10 +13,11 @@
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/scoped_feature_list.h"
 #include "base/test/simple_test_clock.h"
-#include "components/feed/core/pref_names.h"
-#include "components/feed/core/refresh_throttler.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/common/refresh_throttler.h"
+#include "components/feed/core/common/user_classifier.h"
+#include "components/feed/core/shared_prefs/pref_names.h"
 #include "components/feed/core/time_serialization.h"
-#include "components/feed/core/user_classifier.h"
 #include "components/feed/feed_feature_list.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/testing_pref_service.h"
@@ -58,7 +59,7 @@ class FeedSchedulerHostTest : public ::testing::Test {
     local_state()->registry()->RegisterBooleanPref(::prefs::kEulaAccepted,
                                                    true);
     profile_prefs()->registry()->RegisterBooleanPref(
-        prefs::kArticlesListVisible, true);
+        feed::prefs::kArticlesListVisible, true);
 
     Time now;
     EXPECT_TRUE(Time::FromUTCString(kNowString, &now));
@@ -92,7 +93,7 @@ class FeedSchedulerHostTest : public ::testing::Test {
     // into kRareNtpUser classification.
     test_clock()->Advance(TimeDelta::FromDays(7));
 
-    ASSERT_EQ(UserClassifier::UserClass::kRareSuggestionsViewer,
+    ASSERT_EQ(UserClass::kRareSuggestionsViewer,
               scheduler()->GetUserClassifierForDebugging()->GetUserClass());
   }
 
@@ -107,7 +108,7 @@ class FeedSchedulerHostTest : public ::testing::Test {
     // Depending on which events occurred over which period of time in the test
     // before this function was called, it may not necessarily be sufficient to
     // push the user into the active consumer class.
-    ASSERT_EQ(UserClassifier::UserClass::kActiveSuggestionsConsumer,
+    ASSERT_EQ(UserClass::kActiveSuggestionsConsumer,
               scheduler()->GetUserClassifierForDebugging()->GetUserClass());
   }
 
@@ -177,23 +178,22 @@ class FeedSchedulerHostTest : public ::testing::Test {
 TEST_F(FeedSchedulerHostTest, GetTriggerThreshold) {
   // Make sure that there is no missing configuration in the Cartesian product
   // of states between TriggerType and UserClass.
-  std::vector<FeedSchedulerHost::TriggerType> triggers = {
-      FeedSchedulerHost::TriggerType::kNtpShown,
-      FeedSchedulerHost::TriggerType::kForegrounded,
-      FeedSchedulerHost::TriggerType::kFixedTimer};
+  std::vector<TriggerType> triggers = {TriggerType::kNtpShown,
+                                       TriggerType::kForegrounded,
+                                       TriggerType::kFixedTimer};
 
   // Classification starts out as an active NTP user.
-  for (FeedSchedulerHost::TriggerType trigger : triggers) {
+  for (TriggerType trigger : triggers) {
     EXPECT_FALSE(scheduler()->GetTriggerThreshold(trigger).is_zero());
   }
 
   ClassifyAsActiveSuggestionsConsumer();
-  for (FeedSchedulerHost::TriggerType trigger : triggers) {
+  for (TriggerType trigger : triggers) {
     EXPECT_FALSE(scheduler()->GetTriggerThreshold(trigger).is_zero());
   }
 
   ClassifyAsRareNtpUser();
-  for (FeedSchedulerHost::TriggerType trigger : triggers) {
+  for (TriggerType trigger : triggers) {
     EXPECT_FALSE(scheduler()->GetTriggerThreshold(trigger).is_zero());
   }
 }
@@ -1034,14 +1034,14 @@ TEST_F(FeedSchedulerHostTest, RefreshThrottler) {
 TEST_F(FeedSchedulerHostTest, GetUserClassifierForDebuggingRareUser) {
   ClassifyAsRareNtpUser();
 
-  EXPECT_EQ(UserClassifier::UserClass::kRareSuggestionsViewer,
+  EXPECT_EQ(UserClass::kRareSuggestionsViewer,
             scheduler()->GetUserClassifierForDebugging()->GetUserClass());
 }
 
 TEST_F(FeedSchedulerHostTest, GetUserClassifierForDebuggingActiveConsumer) {
   ClassifyAsActiveSuggestionsConsumer();
 
-  EXPECT_EQ(UserClassifier::UserClass::kActiveSuggestionsConsumer,
+  EXPECT_EQ(UserClass::kActiveSuggestionsConsumer,
             scheduler()->GetUserClassifierForDebugging()->GetUserClass());
 }
 
@@ -1069,19 +1069,19 @@ TEST_F(FeedSchedulerHostTest, GetLastFetchStatusForDebugging) {
 TEST_F(FeedSchedulerHostTest, GetLastFetchTriggerTypeForDebugging) {
   scheduler()->OnForegrounded();
 
-  EXPECT_EQ(FeedSchedulerHost::TriggerType::kForegrounded,
+  EXPECT_EQ(TriggerType::kForegrounded,
             *scheduler()->GetLastFetchTriggerTypeForDebugging());
 
   scheduler()->OnArticlesCleared(/*suppress_refreshes*/ false);
 
-  EXPECT_EQ(FeedSchedulerHost::TriggerType::kNtpShown,
+  EXPECT_EQ(TriggerType::kNtpShown,
             *scheduler()->GetLastFetchTriggerTypeForDebugging());
 
   ClassifyAsActiveSuggestionsConsumer();  // Fixed timer at 48 hours.
   test_clock()->Advance(TimeDelta::FromHours(49));
   scheduler()->OnFixedTimer(base::OnceClosure());
 
-  EXPECT_EQ(FeedSchedulerHost::TriggerType::kFixedTimer,
+  EXPECT_EQ(TriggerType::kFixedTimer,
             *scheduler()->GetLastFetchTriggerTypeForDebugging());
 }
 
diff --git a/chromium/components/feed/core/proto/BUILD.gn b/chromium/components/feed/core/proto/BUILD.gn
index 7ceb58bafa7..d9da12241c5 100644
--- a/chromium/components/feed/core/proto/BUILD.gn
+++ b/chromium/components/feed/core/proto/BUILD.gn
@@ -16,6 +16,44 @@ proto_library("proto") {
   ]
 }
 
+proto_library("proto_v2") {
+  proto_in_dir = "../../../../"
+  sources = [
+    "v2/store.proto",
+    "v2/ui.proto",
+    "v2/wire/action_payload.proto",
+    "v2/wire/action_request.proto",
+    "v2/wire/action_response.proto",
+    "v2/wire/capability.proto",
+    "v2/wire/client_info.proto",
+    "v2/wire/consistency_token.proto",
+    "v2/wire/content_id.proto",
+    "v2/wire/data_operation.proto",
+    "v2/wire/display_info.proto",
+    "v2/wire/duration.proto",
+    "v2/wire/expiration_info.proto",
+    "v2/wire/feature.proto",
+    "v2/wire/feed_action.proto",
+    "v2/wire/feed_action_request.proto",
+    "v2/wire/feed_action_response.proto",
+    "v2/wire/feed_id.proto",
+    "v2/wire/feed_query.proto",
+    "v2/wire/feed_request.proto",
+    "v2/wire/feed_response.proto",
+    "v2/wire/in_place_update_handle.proto",
+    "v2/wire/next_page_token.proto",
+    "v2/wire/payload_metadata.proto",
+    "v2/wire/render_data.proto",
+    "v2/wire/request.proto",
+    "v2/wire/response.proto",
+    "v2/wire/response_status_code.proto",
+    "v2/wire/stream_structure.proto",
+    "v2/wire/templates.proto",
+    "v2/wire/token.proto",
+    "v2/wire/version.proto",
+  ]
+}
+
 if (is_android) {
   proto_java_library("proto_java") {
     proto_path = "../../../../"
@@ -75,4 +113,9 @@ if (is_android) {
       "wire/version.proto",
     ]
   }
+
+  proto_java_library("proto_java_v2") {
+    proto_path = "../../../../"
+    sources = [ "v2/ui.proto" ]
+  }
 }
diff --git a/chromium/components/feed/core/proto/libraries/api/internal/stream_data.proto b/chromium/components/feed/core/proto/libraries/api/internal/stream_data.proto
index f506539af59..e66a0b818d7 100644
--- a/chromium/components/feed/core/proto/libraries/api/internal/stream_data.proto
+++ b/chromium/components/feed/core/proto/libraries/api/internal/stream_data.proto
@@ -72,8 +72,7 @@ message StreamSharedState {
   optional string content_id = 1;
   oneof share_state {
     // A Piet shared state item.
-    components.feed.core.proto.wire.PietSharedStateItem piet_shared_state_item =
-        2;
+    feedwire1.PietSharedStateItem piet_shared_state_item = 2;
   }
 }
 
@@ -157,7 +156,7 @@ message StreamPayload {
 
     // The consistency token used to ensure that we are recording actions to
     // the same server store.
-    components.feed.core.proto.wire.ConsistencyToken consistency_token = 9;
+    feedwire1.ConsistencyToken consistency_token = 9;
   }
   reserved 8;
 }
@@ -228,7 +227,7 @@ message StreamUploadableAction {
   // When the action was recorded
   optional int64 timestamp_seconds = 4;
 
-  optional wire.ActionPayload payload = 6;
+  optional feedwire1.ActionPayload payload = 6;
 
   reserved 1, 5;  // deprecated fields
 }
diff --git a/chromium/components/feed/core/proto/ui/action/ui_feed_action.proto b/chromium/components/feed/core/proto/ui/action/ui_feed_action.proto
index ed9766bdfa2..419ea251146 100644
--- a/chromium/components/feed/core/proto/ui/action/ui_feed_action.proto
+++ b/chromium/components/feed/core/proto/ui/action/ui_feed_action.proto
@@ -30,7 +30,7 @@ message FeedAction {
 }
 
 // Metadata needed by the host to handle the action.
-// Next Id: 9
+// Next Id: 19
 message FeedActionMetadata {
   // The type of action, used by the host to perform any custom logic needed for
   // a specific type of action.
@@ -57,6 +57,9 @@ message FeedActionMetadata {
     HIDE_ELEMENT = 13;
     SHOW_TOOLTIP = 14;
     NOT_INTERESTED_IN = 15;
+    SEE_SUGGESTED_SITES = 16;
+    SEND_FEEDBACK = 17;
+    MANAGE_INTERESTS = 18;
     reserved 9, 10;  // Deprecated
   }
   optional Type type = 1;
@@ -102,6 +105,10 @@ message OpenUrlData {
   // opening the url. Once this finishes, the client will attach to the url its
   //  latest frequency token as the value of this query param.
   optional string consistency_token_query_param_name = 2;
+  // The content ID that was interacted with to cause a URL open.
+  optional feedwire1.ContentId content_id = 3;
+  // Roundtripped server data on a per-action level.
+  optional feedwire1.ActionPayload payload = 4;
 }
 
 // Data needed by Stream to open a context menu.
@@ -114,19 +121,19 @@ message DismissData {
   // The ContentId needed by the server to suppress reshowing the dismissed
   // content. This will usually be the ContentId of the card which holds the
   // content, not the ContentId of the content itself.
-  optional components.feed.core.proto.wire.ContentId content_id = 1;
+  optional feedwire1.ContentId content_id = 1;
 
   // The DataOperations which are needed to actually perform the dismiss on the
   // client. This is typically a singleton list of a remove operation on the
   // Cluster that the content belongs to.
-  repeated components.feed.core.proto.wire.DataOperation data_operations = 2;
+  repeated feedwire1.DataOperation data_operations = 2;
 
   // Data used by the client to show a confirmation message with option to undo.
   // This confirmation and undo option will only appear if the UndoAction is
   // present and the client can handle this capability.
   optional UndoAction undo_action = 3;
   // Roundtripped server data on a per-action level.
-  optional components.feed.core.proto.wire.ActionPayload payload = 4;
+  optional feedwire1.ActionPayload payload = 4;
 }
 
 // Data needed by the client to handle the not interested action.
@@ -136,9 +143,9 @@ message NotInterestedInData {
   // present and the client can handle this capability.
   optional UndoAction undo_action = 1;
   // The data needed by Stream to preform the dismiss.
-  repeated components.feed.core.proto.wire.DataOperation data_operations = 2;
+  repeated feedwire1.DataOperation data_operations = 2;
   // Roundtripped server data on a per-action level.
-  optional components.feed.core.proto.wire.ActionPayload payload = 3;
+  optional feedwire1.ActionPayload payload = 3;
   enum RecordedInterestType {
     UNKNOWN_INTEREST_TYPE = 0;
     TOPIC = 1;
diff --git a/chromium/components/feed/core/proto/ui/piet/accessibility.proto b/chromium/components/feed/core/proto/ui/piet/accessibility.proto
index b92fb90073a..b73760bc401 100644
--- a/chromium/components/feed/core/proto/ui/piet/accessibility.proto
+++ b/chromium/components/feed/core/proto/ui/piet/accessibility.proto
@@ -43,6 +43,19 @@ message Accessibility {
     // ID coming from a template.
     ParameterizedTextBindingRef accessibility_id_binding = 5;
   }
+
+  oneof context_data {
+    // A string that may be spoken by the system that describes the result of an
+    // action. For example, "Opens the article." This provides additional
+    // context over the description.
+
+    // NOTE: Only supported by iOS and maps to accessibilityHint on an
+    // accessible element.
+    ParameterizedText context = 6;
+
+    // In case this is coming from a template.
+    ParameterizedTextBindingRef context_binding = 7;
+  }
 }
 
 // Semantic roles played by a UI element related to accessibility.
diff --git a/chromium/components/feed/core/proto/ui/piet/errors.proto b/chromium/components/feed/core/proto/ui/piet/errors.proto
index e5734305482..54e2818e7ba 100644
--- a/chromium/components/feed/core/proto/ui/piet/errors.proto
+++ b/chromium/components/feed/core/proto/ui/piet/errors.proto
@@ -122,6 +122,17 @@ enum ErrorCode {
   // Fields start at ID 1.
   // ---------------------------------------------------------------------------
 
+  // When the client tries to reference a SharedState that is not found, the
+  // Frame cannot be rendered, and likely no frames can be rendered.
+  // This error code must be reported by the Piet host app, as the Piet
+  // implementation assumes that all shared states have been provided already.
+  ERR_MISSING_SHARED_STATE = 12 /* [
+    // Something is seriously wrong if a SharedState is missing
+    (server_error) = FATAL,
+    // Clients cannot render any Frame when SharedState is missing (no Template)
+    (client_error) = FATAL
+  ] */;
+
   // When a Template cannot be located, it only affects Frames that reference
   // it, so we can proceed to render other unaffected Frames, making this an
   // ERROR, not FATAL.
@@ -214,6 +225,14 @@ enum ErrorCode {
     (client_error) = ERROR
   ] */;
 
+  // Bindings are not supported in Frames or within Bound Elements.
+  ERR_UNSUPPORTED_CONTEXT_FOR_BINDING = 11 /* [
+    // Bindings will not work in this context
+    (server_error) = ERROR,
+    // Clients might support bindings in this context.
+    (client_error) = WARNING
+  ] */;
+
   // ---------------------------------------------------------------------------
   // Missing required proto fields, or invalid values.
   // Fields start at ID 101.
diff --git a/chromium/components/feed/core/proto/ui/stream/stream_structure.proto b/chromium/components/feed/core/proto/ui/stream/stream_structure.proto
index b529dbe99cb..f7d4389071d 100644
--- a/chromium/components/feed/core/proto/ui/stream/stream_structure.proto
+++ b/chromium/components/feed/core/proto/ui/stream/stream_structure.proto
@@ -19,9 +19,7 @@ option cc_enable_arenas = true;
 // Top level feature which shows a stream of cards.  Provides any UI information
 // which may be needed in order to render the stream of cards.
 message Stream {
-  extend components.feed.core.proto.wire.Feature {
-    optional Stream stream_extension = 185431437;
-  }
+  extend feedwire1.Feature { optional Stream stream_extension = 185431437; }
 
   // Empty for now as don't support any custom information.
 }
@@ -29,9 +27,7 @@ message Stream {
 // Feature which represents a cluster in a Stream. May have a Card or Content
 // as children.
 message Cluster {
-  extend components.feed.core.proto.wire.Feature {
-    optional Cluster cluster_extension = 190812910;
-  }
+  extend feedwire1.Feature { optional Cluster cluster_extension = 190812910; }
 
   // Empty for now as we don't support any custom information.
 }
@@ -39,9 +35,7 @@ message Cluster {
 // Experimental feature which represents a carousel in a Stream. May have a list
 // of Cards or Content as children.
 message Carousel {
-  extend components.feed.core.proto.wire.Feature {
-    optional Carousel carousel_extension = 244251946;
-  }
+  extend feedwire1.Feature { optional Carousel carousel_extension = 244251946; }
 
   // Please use CL numbers you own for extension numbers.
   extensions 10000 to max;
@@ -50,9 +44,7 @@ message Carousel {
 // Feature which represents a full card in a Stream.  Allows metadata to be sent
 // to describe how to render the card.
 message Card {
-  extend components.feed.core.proto.wire.Feature {
-    optional Card card_extension = 185431438;
-  }
+  extend feedwire1.Feature { optional Card card_extension = 185431438; }
 
   // Please use CL numbers you own for extension numbers.
   extensions 10000 to max;
@@ -98,9 +90,7 @@ message OfflineMetadata {
 // inside or outside a card. Actual data on what to display will be sent on an
 // extension.
 message Content {
-  extend components.feed.core.proto.wire.Feature {
-    optional Content content_extension = 185431439;
-  }
+  extend feedwire1.Feature { optional Content content_extension = 185431439; }
 
   enum Type {
     UNKNOWN_CONTENT = 0;
@@ -122,7 +112,7 @@ message PietContent {
 
   // Content Ids of Piet Shared States which should be provided to Piet in order
   // to show its content.
-  repeated components.feed.core.proto.wire.ContentId piet_shared_states = 1;
+  repeated feedwire1.ContentId piet_shared_states = 1;
 
   // The Piet frame to render.
   optional components.feed.core.proto.ui.piet.Frame frame = 2;
diff --git a/chromium/components/feed/core/proto/v2/store.proto b/chromium/components/feed/core/proto/v2/store.proto
new file mode 100644
index 00000000000..99df5c61363
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/store.proto
@@ -0,0 +1,173 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto3";
+
+package feedstore;
+
+import "components/feed/core/proto/v2/wire/content_id.proto";
+import "components/feed/core/proto/v2/wire/feed_action.proto";
+
+option optimize_for = LITE_RUNTIME;
+
+// Actual data stored by the client.
+// This data is sourced from the wire protocol, which is converted upon receipt.
+// This would replace both Journal and Content stores.
+//
+// This is the 'value' in the key/value store.
+// Keys are defined as:
+// 'S/<stream-id>' -> stream_data
+// 'T/<stream-id>/<sequence-number>' -> stream_structures
+// 'c/<content-id>' -> content
+// 'a/<id>' -> action
+// 's/<content-id>' -> shared_state
+// 'N' -> next_stream_state
+message Record {
+  oneof data {
+    StreamData stream_data = 1;
+    StreamStructureSet stream_structures = 2;
+    Content content = 3;
+    StoredAction local_action = 4;
+    StreamSharedState shared_state = 5;
+    // The result of a background refresh, to be processed later.
+    StreamAndContentState next_stream_state = 6;
+  }
+}
+
+// Data about the Feed stream. There is at most one instance of StreamData.
+message StreamData {
+  // Root ContentId, as provided by the server.
+  feedwire.ContentId content_id = 1;
+  // Token used to request a 'more' request to the server.
+  bytes next_page_token = 2;
+  // Token used to read or write to the same storage.
+  bytes consistency_token = 3;
+  // The unix timestamp in milliseconds that the most recent content was added.
+  int64 last_added_time_millis = 4;
+  // Next sequential ID to be used for StoredAction.id.
+  int32 next_action_id = 5;
+  // The content ID of the shared state for this stream.
+  feedwire.ContentId shared_state_id = 6;
+}
+
+// A set of StreamStructures that should be applied to a stream.
+message StreamStructureSet {
+  string stream_id = 1;
+  int32 sequence_number = 2;
+  repeated StreamStructure structures = 3;
+}
+
+// This is the structure of the stream.  It is defined through the parent/child
+// relationship and an operation.  This message will be journaled.  Reading
+// the journal from start to end will fully define the structure of the stream.
+message StreamStructure {
+  // The defined set of DataOperations
+  // These operations align with the Operation enum defined in
+  // data_operation.proto.
+  enum Operation {
+    UNKNOWN = 0;
+    // Clear all the content in the session, creating a new session
+    CLEAR_ALL = 1;
+    // Append if not present or update
+    UPDATE_OR_APPEND = 2;
+    // Remove the node from its parent
+    REMOVE = 3;
+  }
+  Operation operation = 1;
+  // The ContentId of the content.
+  feedwire.ContentId content_id = 2;
+  // The parent ContentId, or unset if this is the root.
+  feedwire.ContentId parent_id = 3;
+
+  // Type of node as denoted by the server. This type has no meaning for the
+  // client.
+  enum Type {
+    // Default type for operations that don't affect the stream (e.g. operations
+    // on shared states).
+    UNKNOWN_TYPE = 0;
+    // The root of the stream.
+    STREAM = 1;
+    // An internal tree node, which may have children.
+    CARD = 2;
+    // A leaf node, which provides content.
+    CONTENT = 3;
+    // An internal tree node, which may have children.
+    CLUSTER = 4;
+  }
+  Type type = 4;
+  // Set iff type=CONTENT
+  ContentInfo content_info = 5;
+}
+
+message DataOperation {
+  StreamStructure structure = 1;
+  // Provided if structure adds content.
+  Content content = 2;
+}
+
+message RepresentationData {
+  // URI (usually a URL) of what the content links to
+  string uri = 1;
+  // Unix timestamp (seconds) when content was published
+  int64 published_time_seconds = 2;
+}
+
+message ContentInfo {
+  // Score given by server.
+  float score = 1;
+  // Unix timestamp (seconds) that content was received by Chrome.
+  int64 availability_time_seconds = 2;
+  RepresentationData representation_data = 3;
+  OfflineMetadata offline_metadata = 4;
+}
+
+message OfflineMetadata {
+  // Title of the content.
+  string title = 1;
+
+  // Url for image for the content.
+  string image_url = 2;
+
+  // Publisher of the content.
+  string publisher = 3;
+
+  // Url for the favicon for the content.
+  string favicon_url = 4;
+
+  // Short string from the content, typically the start of an article.
+  string snippet = 5;
+}
+
+message Content {
+  feedwire.ContentId content_id = 1;
+  // Opaque content. The UI layer knows how to parse and render this as a slice.
+  bytes frame = 2;
+}
+
+// This represents a shared state item.
+message StreamSharedState {
+  feedwire.ContentId content_id = 1;
+  // Opaque data required to render content.
+  bytes shared_state_data = 2;
+}
+
+// A stored action awaiting upload.
+message StoredAction {
+  // Unique ID for this stored action, provided by the client.
+  // This is a sequential number, so that the action with the lowest id value
+  // was recorded chronologically first.
+  int32 id = 1;
+  // How many times we have tried to upload the action.
+  int32 upload_attempt_count = 2;
+  // The action to upload.
+  feedwire.FeedAction action = 3;
+}
+
+// The internal version of the server response. Includes feature tree and
+// content.
+message StreamAndContentState {
+  StreamData stream_data = 1;
+  repeated Content content = 2;
+  repeated StreamSharedState shared_state = 3;
+}
diff --git a/chromium/components/feed/core/proto/v2/ui.proto b/chromium/components/feed/core/proto/v2/ui.proto
new file mode 100644
index 00000000000..c1258bc010b
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/ui.proto
@@ -0,0 +1,110 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto3";
+
+package feedui;
+
+option optimize_for = LITE_RUNTIME;
+
+option java_package = "org.chromium.components.feed.proto";
+option java_outer_classname = "FeedUiProto";
+
+// This is a simplified and complete set of protos that define UI.
+// It includes everything from search.now.ui needed in the UI, and excludes
+// other data to reduce complexity. These proto messages should be constructible
+// from the store protos.
+
+// A stream is a list of chunks in order.
+// Each StreamUpdate contains the full list of chunks,
+// but subsequent StreamUpdates after the first may refer to
+// chunks previously received by chunk_id.
+message StreamUpdate {
+  // Either a reference to an existing slice, or a new slice.
+  message SliceUpdate {
+    oneof update {
+      Slice slice = 1;
+      string slice_id = 2;
+    }
+  }
+  // One entry for each slice in the stream, in the order they should be
+  // presented. Existing slices not present in updated_slices should be dropped.
+  repeated SliceUpdate updated_slices = 1;
+  // Additional shared states to be used. Usually just one, and sent only on the
+  // first update.
+  repeated SharedState new_shared_states = 2;
+}
+
+// A horizontal slice of UI to be presented in the vertical-scrolling feed.
+message Slice {
+  oneof SliceData {
+    XSurfaceSlice xsurface_slice = 1;
+    ZeroStateSlice zero_state_slice = 3;
+  }
+  string slice_id = 2;
+}
+
+// This slice is sent when no feed data can be loaded.
+message ZeroStateSlice {
+  enum Type {
+    UNKNOWN = 0;
+    // A generic error that explains there are no cards available.
+    NO_CARDS_AVAILABLE = 1;
+    // An error indicating there were problems refreshing the feed.
+    CANT_REFRESH = 2;
+  };
+  Type type = 1;
+}
+
+message XSurfaceSlice {
+  bytes xsurface_frame = 1;
+}
+
+// Wraps an XSurface shared state with a unique ID.
+message SharedState {
+  string id = 1;
+  bytes xsurface_shared_state = 2;
+}
+
+// An event on the UI.
+message UiEvent {
+  enum Type {
+    UNKNOWN = 0;
+    CARD_TAPPED = 1;
+    CARD_VIEWED = 2;
+    CARD_SWIPED = 3;
+    MORE_BUTTON_VIEWED = 4;
+    MORE_BUTTON_CLICKED = 5;
+    SPINNER_STARTED = 6;
+    SPINNER_FINISHED = 7;
+    SPINNER_DESTROYED_WITHOUT_COMPLETING = 8;
+    PIET_FRAME_RENDERING_EVENT = 9;
+    SCROLL_STREAM = 10;
+  }
+  enum SpinnerType {
+    UNKNOWN_SPINNER_TYPE = 0;
+    // Spinner shown on initial load of the Feed.
+    INITIAL_LOAD = 1;
+    // Spinner shown when Feed is refreshed.
+    ZERO_STATE_REFRESH = 2;
+    // Spinner shown when more button is clicked.
+    MORE_BUTTON = 3;
+    // Spinner shown when a synthetic token is consumed.
+    SYNTHETIC_TOKEN = 4;
+    // Spinner shown when a spinner is shown for loading the infinite feed.
+    INFINITE_FEED = 5;
+  }
+  // For CARD_* type events.
+  string chunk_id = 1;
+  // For MORE_BUTTON_* type events.
+  int32 more_button_position = 2;
+  // For SPINNER_* type events.
+  SpinnerType spinner_type = 3;
+  // For SPINNER_FINISHED and SPINNER_DESTROYED_WITHOUT_COMPLETING.
+  int32 spinner_time_shown = 4;
+  // For PIET_FRAME_RENDERING_EVENT.
+  repeated int32 piet_error_codes = 5;
+  // For SCROLL_STREAM.
+  int32 scroll_distance = 6;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/action_payload.proto b/chromium/components/feed/core/proto/v2/wire/action_payload.proto
new file mode 100644
index 00000000000..cc072bfb427
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/action_payload.proto
@@ -0,0 +1,21 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// The data needed by the server to handle action recording. This information is
+// opaque to the client and will be the information that is round-tripped so the
+// server can properly handle the action. For the Not Interested In action, this
+// data will contain the ids needed to record that the user is not interested
+// in that particular topic or source.
+// NOTE: it is important to keep this to a bare minimum amount of data.
+message ActionPayload {
+  // Reserved fields for renderable unit extensions
+  // Please use CL numbers you own for extension numbers.
+  extensions 257605906;  // ActionPayloadData
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/action_request.proto b/chromium/components/feed/core/proto/v2/wire/action_request.proto
new file mode 100644
index 00000000000..784a50dea03
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/action_request.proto
@@ -0,0 +1,25 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/feed_action_request.proto";
+
+// Top level request message.
+message ActionRequest {
+  // Supported versions of request messages are specified as extensions to
+  // the top-level request message.  An enum is used to denote the expected
+  // extensions for this request.
+  enum RequestVersion {
+    UNKNOWN_ACTION_REQUEST_VERSION = 0;
+    FEED_UPLOAD_ACTION = 1;
+  }
+  optional RequestVersion request_version = 1;
+
+  optional FeedActionRequest feed_action_request = 1000;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/action_response.proto b/chromium/components/feed/core/proto/v2/wire/action_response.proto
new file mode 100644
index 00000000000..213bf3a7473
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/action_response.proto
@@ -0,0 +1,23 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Top level response message.
+message ActionResponse {
+  // Supported versions of response messages are specified as extensions to
+  // the top-level response message.  An enum is used to denote the expected
+  // extensions for this response.
+  enum ResponseVersion {
+    UNKNOWN_ACTION_RESPONSE_VERSION = 0;
+    FEED_UPLOAD_ACTION_RESPONSE = 1;
+  }
+  optional ResponseVersion response_version = 1;
+
+  extensions 1000;  // FeedActionResponse
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/capability.proto b/chromium/components/feed/core/proto/v2/wire/capability.proto
new file mode 100644
index 00000000000..73b95309fda
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/capability.proto
@@ -0,0 +1,39 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Feature capability of either the client or the server.
+// Next ID: 20
+enum Capability {
+  UNKNOWN_CAPABILITY = 0;
+  // The client is capable of a basic UI.
+  BASE_UI = 1;
+
+  INFINITE_FEED = 5;
+  // Enable Dismiss command
+  DISMISS_COMMAND = 9;
+  // Enable Undo in Dismiss
+  UNDO_FOR_DISMISS_COMMAND = 10;
+  REDACTED_11 = 11;
+  // The client is only considered capable of supporting a minimal heirloomed
+  // feed.
+  HEIRLOOMED_FEED = 13;
+  // The client is capable of supporting sports features.
+  SPORTS_FEATURE = 14;
+  // The client is capable of supporting ads content.
+  PAID_CONTENT = 15;
+  // Enable open video command.
+  OPEN_VIDEO_COMMAND = 16;
+  REDACTED_17 = 17;
+  // Enable inline video autoplay.
+  INLINE_VIDEO_AUTOPLAY = 18;
+  // Enable the card menu.
+  CARD_MENU = 19;
+  reserved 2 to 4, 6 to 8, 12;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/client_info.proto b/chromium/components/feed/core/proto/v2/wire/client_info.proto
new file mode 100644
index 00000000000..a4e7753cd34
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/client_info.proto
@@ -0,0 +1,61 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/display_info.proto";
+import "components/feed/core/proto/v2/wire/version.proto";
+
+// Information about the client performing the request similar to a user-agent
+// string in HTTP.
+// Next ID: 10.
+message ClientInfo {
+  enum PlatformType {
+    UNKNOWN_PLATFORM = 0;
+    ANDROID_ID = 1;  // ANDROID collides with a C++ preprocessor macro.
+    IOS = 2;
+  }
+
+  enum AppType { CHROME = 3; }
+
+  // The type of OS that the client is running.
+  optional PlatformType platform_type = 1;
+
+  // The version of the OS that the client is running.
+  optional Version platform_version = 2;
+
+  // The type of client app.
+  optional AppType app_type = 3;
+
+  // The version of the client app.
+  optional Version app_version = 4;
+
+  // A string identifying the language and region preferences of the client.
+  // Follows the BCP 47 format such as "en-US" or "fr-CA"
+  optional string locale = 5;
+
+  // The information about the screen of the client. This is repeated because
+  // there are some devices that might have multiple display screens.
+  // (Ex fold-able phones)
+  repeated DisplayInfo display_info = 6;
+
+  // Identifier of the user's device. For Android devices, contains a hash of
+  // the gaia email and android_id, which uniquely identifies the device for
+  // the user. Currently set by Android clients version 4.1 and later.
+  optional string client_instance_id = 7;
+
+  // An Android device level identifier used for advertising, required for
+  // conversion tracking, see more at:
+  // https://support.google.com/googleplay/android-developer/answer/6048248
+  optional string advertising_id = 8;
+
+  // Two-letter country code as detected by the device. On Android devices,
+  // this comes from GServices check-in which uses the SIM card MCC (mobile
+  // country code), with fallback to IP geo lookup.
+  optional string device_country = 9;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/consistency_token.proto b/chromium/components/feed/core/proto/v2/wire/consistency_token.proto
new file mode 100644
index 00000000000..48a6b2028bd
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/consistency_token.proto
@@ -0,0 +1,15 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// A consistency token.
+message ConsistencyToken {
+  // Indicates the min version of storage to read from.
+  optional bytes token = 1;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/content_id.proto b/chromium/components/feed/core/proto/v2/wire/content_id.proto
new file mode 100644
index 00000000000..b098b3092f1
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/content_id.proto
@@ -0,0 +1,49 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// An identifier for a piece of content served by Now or delivered to the Now
+// client(s).
+// See [INTERNAL LINK] for the design of this feature.
+// ContentId comprises a unique key for all content. The client will never have
+// more than one piece of content with the same ContentID.
+message ContentId {
+  optional string content_domain = 1;
+
+  // The type of content this represents. Generally, this is somewhat redundant,
+  // as this ContentId proto will be embedded within a particular parent proto
+  // that implies its type. It is repeated here for the purpose of making
+  // ContentId fully self-contained, able to completely specify a piece of
+  // content's ID without additional context.
+  // Since Type is one of the components of content's uniqueness, it is safe
+  // and reasonable for two related pieces of content with different types
+  // (e.g. a card and its attached notification) to share the same id and
+  // content_domain, and to differ only in their type.  However, Type is **not**
+  // included when determing if two ContentIds are equivalent.
+  enum Type {
+    // Undefined type - DO NOT USE
+    TYPE_UNDEFINED = 0;
+    CARD = 1;
+    CLUSTER = 3;
+    // A feature, which is the indivisible unit of Feed content.
+    FEATURE = 4;
+    // A ContentId used only for identifying nodes in a tree structure.
+    TREE_STRUCTURE = 7;
+    // A ContentId for a collection.
+    COLLECTION = 8;
+    // A ContentId for a token, e.g. a NextPage token.
+    TOKEN = 9;
+
+    reserved 2;
+  }
+  // The type of content this represents
+  optional Type type = 2;
+
+  optional fixed64 id = 3;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/data_operation.proto b/chromium/components/feed/core/proto/v2/wire/data_operation.proto
new file mode 100644
index 00000000000..0651eb21797
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/data_operation.proto
@@ -0,0 +1,55 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/feature.proto";
+import "components/feed/core/proto/v2/wire/in_place_update_handle.proto";
+import "components/feed/core/proto/v2/wire/payload_metadata.proto";
+import "components/feed/core/proto/v2/wire/render_data.proto";
+import "components/feed/core/proto/v2/wire/templates.proto";
+import "components/feed/core/proto/v2/wire/token.proto";
+
+// An extensible operation to change the state of data on the client.
+message DataOperation {
+  // Next tag: 8
+
+  enum Operation {
+    UNKNOWN_OPERATION = 0;
+    // Remove all stored content of all types
+    CLEAR_ALL = 1;
+    // Update content if it exists, else append to the bottom of the feed
+    UPDATE_OR_APPEND = 2;
+    // Remove the item from the stream
+    REMOVE = 3;
+  }
+
+  // The operation to perform on the data.
+  optional Operation operation = 1;
+
+  // Data common to all payload types.
+  optional PayloadMetadata metadata = 2;
+
+  // The actual data being supplied.
+  oneof payload {
+    // A stream UI level feature such as a cluster or card.
+    Feature feature = 3;
+
+    // A token, capable of making a next page request.
+    Token next_page_token = 5;
+
+    // Information to help render the content in the response.
+    RenderData render_data = 6;
+
+    // A handle for updating one or more pieces of content in place.
+    InPlaceUpdateHandle in_place_update_handle = 8;
+
+    // A collection of templates.
+    Templates templates = 4 [deprecated = true];
+  }
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/display_info.proto b/chromium/components/feed/core/proto/v2/wire/display_info.proto
new file mode 100644
index 00000000000..f12bc749e8a
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/display_info.proto
@@ -0,0 +1,24 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// The information about the client's screen.
+// Next id: 4
+message DisplayInfo {
+  // Density of the screen in physical pixels per density independent pixel
+  // (DIP); see:
+  // http://developer.android.com/reference/android/util/DisplayMetrics.html#density
+  optional float screen_density = 1;
+
+  // The width of the screen in pixels.
+  optional uint32 screen_width_in_pixels = 2;
+
+  // The height of the screen in pixels.
+  optional uint32 screen_height_in_pixels = 3;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/duration.proto b/chromium/components/feed/core/proto/v2/wire/duration.proto
new file mode 100644
index 00000000000..5f261ae32bc
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/duration.proto
@@ -0,0 +1,15 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto3";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Copy of third_party/protobuf/src/google/protobuf/duration.proto.
+message Duration {
+  int64 seconds = 1;
+  int32 nanos = 2;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/expiration_info.proto b/chromium/components/feed/core/proto/v2/wire/expiration_info.proto
new file mode 100644
index 00000000000..326ceb86093
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/expiration_info.proto
@@ -0,0 +1,26 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/duration.proto";
+
+/* Information about whether and when a feature should expire and be removed
+ * from Discover. */
+message ExpirationInfo {
+  // Whether the feature can expire.
+  optional bool should_expire = 1;
+
+  // Indicates how long after this response was received the client should wait
+  // before expiring (and hiding) this content. This expiration time is a best
+  // effort, and should not be done while the content is visible on screen.
+  // There are no penalties with showing the content after the expiry, though
+  // some uses of this API (ads in particular) do have SLA's about how often
+  // items can be shown after expiration.
+  optional feedwire.Duration expiration_duration = 2;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feature.proto b/chromium/components/feed/core/proto/v2/wire/feature.proto
new file mode 100644
index 00000000000..775961cec7f
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feature.proto
@@ -0,0 +1,47 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/content_id.proto";
+import "components/feed/core/proto/v2/wire/expiration_info.proto";
+import "components/feed/core/proto/v2/wire/stream_structure.proto";
+
+// Features define both the structure and content found in the Stream.
+message Feature {
+  // The ContentId identifying the parent feature for this feature.
+  optional ContentId parent_id = 1;
+
+  // Enum denoting which extension containing the renderable data is associated
+  // with this Feature.
+  enum RenderableUnit {
+    UNKNOWN_RENDERABLE_UNIT = 0;
+    STREAM = 1;
+    CONTENT = 3;
+    CLUSTER = 4;
+    REDACTED_10 = 10;
+    REDACTED_11 = 11;
+    reserved 2, 5, 6, 7, 8, 9;
+  }
+  optional RenderableUnit renderable_unit = 2;
+
+  // Indicates whether this feature should expire, and additional metadata
+  // necessariy to handle expiration. Note that clients may not support
+  // expiration of every type of feature.
+  optional ExpirationInfo expiration_info = 3;
+
+  optional Stream stream_extension = 185431437;
+  optional Cluster cluster_extension = 190812910;
+  extensions 185431438;  // Card
+  optional Content content_extension = 185431439;
+  extensions 194964015;  // Token
+  extensions 286406442;  // REDACTED
+  extensions 286406443;  // REDACTED
+
+  reserved 246375740, 274598443, 274598444, 277068786;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_action.proto b/chromium/components/feed/core/proto/v2/wire/feed_action.proto
new file mode 100644
index 00000000000..62ae63efbc4
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_action.proto
@@ -0,0 +1,38 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/action_payload.proto";
+import "components/feed/core/proto/v2/wire/content_id.proto";
+
+message FeedAction {
+  // The Id for the content that this action was triggered on.
+  optional ContentId content_id = 1;
+  // Additional logging data that is on a per-action level
+  optional ActionPayload action_payload = 2;
+  // Client-generated data that pertains to the action.
+  optional ClientData client_data = 3;
+  // Next Id: 7
+
+  // The data the client provides to the server.
+  message ClientData {
+    // When the action was recorded on the client
+    optional int64 timestamp_seconds = 1;
+
+    // A monotonically-increasing sequence number that increments per
+    // user + device. Used in experiments to measure action loss between client
+    // and server.
+    optional int64 sequence_number = 2;
+
+    // The duration for the action in milliseconds. In case of view actions this
+    // is the duration for which the content is considered "viewed".
+    optional int64 duration_ms = 3;
+  }
+  reserved 4, 5, 6;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_action_request.proto b/chromium/components/feed/core/proto/v2/wire/feed_action_request.proto
new file mode 100644
index 00000000000..f57f328fc0b
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_action_request.proto
@@ -0,0 +1,20 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/consistency_token.proto";
+import "components/feed/core/proto/v2/wire/feed_action.proto";
+
+// Request to upload new actions to the Actions Endpoint
+message FeedActionRequest {
+  // Data related to recordable actions performed on the client.
+  repeated FeedAction feed_action = 1;
+  // Token used to write to the same storage.
+  optional ConsistencyToken consistency_token = 2;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_action_response.proto b/chromium/components/feed/core/proto/v2/wire/feed_action_response.proto
new file mode 100644
index 00000000000..0cb782bd79a
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_action_response.proto
@@ -0,0 +1,18 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/consistency_token.proto";
+
+// A feed action response returns when an action has been successfully uploaded
+// to the server.
+message FeedActionResponse {
+  // Token used to read or write to the same storage.
+  optional ConsistencyToken consistency_token = 1;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_id.proto b/chromium/components/feed/core/proto/v2/wire/feed_id.proto
new file mode 100644
index 00000000000..25afaa860b4
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_id.proto
@@ -0,0 +1,20 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// This proto is used to uniquely identify a Feed of cards.
+// The main use case is for the paginated feed, storing multiple
+// feeds on the server, and needing to identify them individually.
+// It is an empty extension holder because the client should not ever know
+// or care what's in the FeedId, and so we can change the definition
+// of what a FeedId for the server without worrying about users possibly
+// looking into the implementation details.
+message FeedId {
+  extensions 1 to 6;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_query.proto b/chromium/components/feed/core/proto/v2/wire/feed_query.proto
new file mode 100644
index 00000000000..e69e919fae6
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_query.proto
@@ -0,0 +1,52 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/token.proto";
+
+message FeedQuery {
+  enum RequestReason {
+    // Bucket for any not listed. Should not be used (prefer adding a new
+    // request reason)
+    UNKNOWN_REQUEST_REASON = 0;
+
+    // App is manually triggering a request, outside of scheduling a request.
+    // Should be used rarely.
+    MANUAL_REFRESH = 1;
+
+    // Host wants a request to refresh content.
+    SCHEDULED_REFRESH = 2;
+
+    // Host wants a request to load more content.
+    NEXT_PAGE_SCROLL = 3;
+
+    REDACTED_4 = 4;
+
+    // Host wants to update content in place.
+    IN_PLACE_UPDATE = 5;
+  }
+
+  // The reason the query is being initiated.
+  optional RequestReason reason = 1;
+
+  // A collection of Token messages, wrapped in a message so it can be used in a
+  // oneof.
+  message Tokens { repeated Token tokens = 1; }
+
+  oneof token {
+    // The token for requesting the next page of Feed content, to be used with
+    // reason = NEXT_PAGE_SCROLL.
+    Token next_page_token = 3;
+    // Tokens from InPlaceUpdateHandle for content to update in place, if
+    // reason = IN_PLACE_UPDATE.
+    Tokens in_place_update_tokens = 5;
+  }
+
+  reserved 2;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_request.proto b/chromium/components/feed/core/proto/v2/wire/feed_request.proto
new file mode 100644
index 00000000000..b4ee427b6dc
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_request.proto
@@ -0,0 +1,37 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/capability.proto";
+import "components/feed/core/proto/v2/wire/client_info.proto";
+import "components/feed/core/proto/v2/wire/consistency_token.proto";
+import "components/feed/core/proto/v2/wire/feed_id.proto";
+import "components/feed/core/proto/v2/wire/feed_query.proto";
+
+// Request to fetch new data for the feed
+message FeedRequest {
+  // Information about the client making the request.
+  optional ClientInfo client_info = 1;
+
+  // Query parameters to fetch feed data.
+  optional FeedQuery feed_query = 2;
+
+  // The list of client supported capabilities.
+  repeated Capability client_capability = 4;
+
+  // Token used to read from/write to the same storage.
+  optional ConsistencyToken consistency_token = 5;
+
+  // Created on the server and used by the client to identify the feed when
+  // clients will store multiple infinite feeds.
+  // See [INTERNAL LINK]
+  repeated FeedId feed_ids_to_preserve = 12;
+
+  reserved 3, 13;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/feed_response.proto b/chromium/components/feed/core/proto/v2/wire/feed_response.proto
new file mode 100644
index 00000000000..c408d59b387
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/feed_response.proto
@@ -0,0 +1,48 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/capability.proto";
+import "components/feed/core/proto/v2/wire/feed_action_response.proto";
+import "components/feed/core/proto/v2/wire/data_operation.proto";
+import "components/feed/core/proto/v2/wire/feed_id.proto";
+import "components/feed/core/proto/v2/wire/response_status_code.proto";
+
+// A feed response is  a series of directives to manipulate backend storage,
+// similar to database commands.  Individual data operations contain all the
+// necessary information to manipulate the client state.
+message FeedResponse {
+  optional FeedActionResponse feed_response = 1000;
+
+  // DataOperations are applied on the client in order in which they are
+  // received.
+  repeated DataOperation data_operation = 1;
+  // Metadata for the entire FeedResponse.
+  optional FeedResponseMetadata feed_response_metadata = 2;
+
+  // The list of server-response supported capabilities.
+  repeated Capability server_capabilities = 3;
+
+  // The status code for this response.
+  optional ResponseStatusCode response_status_code = 4;
+}
+
+// Data which is relevant for the whole response made by the server.
+message FeedResponseMetadata {
+  // Time at which the server fulfilled this response. This is needed as client
+  // cannot be the source of truth.
+  optional int64 response_time_ms = 1;
+
+  // Created on the server and used by the client to identify the feed when
+  // clients will store multiple infinite feeds.
+  // See [INTERNAL LINK]
+  optional FeedId feed_id = 3;
+
+  reserved 2;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/in_place_update_handle.proto b/chromium/components/feed/core/proto/v2/wire/in_place_update_handle.proto
new file mode 100644
index 00000000000..382dcad03d3
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/in_place_update_handle.proto
@@ -0,0 +1,26 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/duration.proto";
+import "components/feed/core/proto/v2/wire/token.proto";
+
+// InPlaceUpdateHandle is a handle for the client to send to the server in order
+// to update content in-place.
+message InPlaceUpdateHandle {
+  // Indicates how long after this response ws received the client should wait
+  // before sending the token back to the server. It is not an error to send the
+  // token earlier, but in that case the server may just replace the handle with
+  // and an updated use_after and the same token.
+  optional feedwire.Duration use_after = 1;
+
+  // Opaque token to use in a request for the server to send updated versions of
+  // its associated content.
+  optional Token token = 2;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/next_page_token.proto b/chromium/components/feed/core/proto/v2/wire/next_page_token.proto
new file mode 100644
index 00000000000..37d532db4ef
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/next_page_token.proto
@@ -0,0 +1,13 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+message NextPageToken {
+  optional bytes next_page_token = 1;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/payload_metadata.proto b/chromium/components/feed/core/proto/v2/wire/payload_metadata.proto
new file mode 100644
index 00000000000..28a7695af40
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/payload_metadata.proto
@@ -0,0 +1,19 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/content_id.proto";
+
+// Metadata common to all payloads in a DataOperation.
+message PayloadMetadata {
+  // The unique identifier of the payload.
+  optional ContentId content_id = 1;
+
+  reserved 2, 3, 4, 5;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/render_data.proto b/chromium/components/feed/core/proto/v2/wire/render_data.proto
new file mode 100644
index 00000000000..67bf2029043
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/render_data.proto
@@ -0,0 +1,23 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Contains data to use during client-side rendering of the response, like
+// templates and themes.
+message RenderData {
+  // Enum denoting which extension contains the render data.
+  enum RenderDataType {
+    UNKNOWN_RENDER_DATA_TYPE = 0;
+    XSURFACE = 1;
+  }
+  optional RenderDataType render_data_type = 1;
+
+  message XSurfaceContainer { optional bytes render_data = 1; }
+  optional XSurfaceContainer xsurface_container = 1000;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/request.proto b/chromium/components/feed/core/proto/v2/wire/request.proto
new file mode 100644
index 00000000000..7add283ffd5
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/request.proto
@@ -0,0 +1,25 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/feed_request.proto";
+
+// Top level request message.
+message Request {
+  // Supported versions of request messages are specified as extensions to
+  // the top-level request message.  An enum is used to denote the expected
+  // extensions for this request.
+  enum RequestVersion {
+    UNKNOWN_REQUEST_VERSION = 0;
+    FEED_QUERY = 1;
+  }
+  optional RequestVersion request_version = 1;
+
+  optional FeedRequest feed_request = 1000;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/response.proto b/chromium/components/feed/core/proto/v2/wire/response.proto
new file mode 100644
index 00000000000..3b87e7e2085
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/response.proto
@@ -0,0 +1,25 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/feed_response.proto";
+
+// Top level response message.
+message Response {
+  // Supported versions of response messages are specified as extensions to
+  // the top-level response message.  An enum is used to denote the expected
+  // extensions for this response.
+  enum ResponseVersion {
+    UNKNOWN_RESPONSE_VERSION = 0;
+    FEED_RESPONSE = 1;
+  }
+  optional ResponseVersion response_version = 1;
+
+  optional FeedResponse feed_response = 1000;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/response_status_code.proto b/chromium/components/feed/core/proto/v2/wire/response_status_code.proto
new file mode 100644
index 00000000000..ec45adb7ff3
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/response_status_code.proto
@@ -0,0 +1,23 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Status for the Feed response.
+enum ResponseStatusCode {
+  UNKNOWN_STATUS_CODE = 0;
+
+  // Eligible for feed and no errors encountered.
+  STATUS_OK = 1;
+
+  // Ineligible for Feed.
+  STATUS_INELIGIBLE_FOR_FEED = 2;
+
+  // No cards.
+  STATUS_NO_CONTENT_RETURNED = 3;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/stream_structure.proto b/chromium/components/feed/core/proto/v2/wire/stream_structure.proto
new file mode 100644
index 00000000000..256aa6c89af
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/stream_structure.proto
@@ -0,0 +1,43 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Top level feature which shows a stream of cards.  Provides any UI information
+// which may be needed in order to render the stream of cards.
+message Stream {
+}
+
+// Feature which represents a cluster in a Stream. May have a Card or Content
+// as children.
+// TODO Determine if Clusters can be removed.
+message Cluster {
+  // Empty for now as we don't support any custom information.
+}
+
+// Feature which is able to show actual content in a stream. This could be
+// inside or outside a card. Actual data on what to display will be sent on an
+// extension.
+message Content {
+  enum Type {
+    UNKNOWN_CONTENT = 0;
+    XSURFACE = 1;
+  }
+  optional Type type = 1;
+
+  optional bool is_ad = 3;
+
+  optional XSurfaceContent xsurface_content = 1000;
+
+  reserved 2;
+}
+
+// Opaque data to for rendering a piece of content.
+message XSurfaceContent {
+  optional bytes xsurface_output = 1;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/templates.proto b/chromium/components/feed/core/proto/v2/wire/templates.proto
new file mode 100644
index 00000000000..ad8ec10b631
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/templates.proto
@@ -0,0 +1,24 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Templates provide a way to separate formatting from content.
+// Deprecated: use RenderData instead.
+message Templates {
+  option deprecated = true;
+
+  // Enum denoting which extension contains template data.
+  enum TemplateType {
+    UNKNOWN_TEMPLATE_TYPE = 0;
+    XSURFACE = 1;
+  }
+  optional TemplateType template_type = 1;
+
+  extensions 264680549;  // XSurfaceTemplates
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/token.proto b/chromium/components/feed/core/proto/v2/wire/token.proto
new file mode 100644
index 00000000000..37e91678636
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/token.proto
@@ -0,0 +1,25 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+import "components/feed/core/proto/v2/wire/content_id.proto";
+import "components/feed/core/proto/v2/wire/next_page_token.proto";
+
+// A structure containing client-opaque data relating to a request.
+message Token {
+  // The ContentId identifying the parent for this feature. Needed for tokens
+  // used in a data operation.
+  optional ContentId parent_id = 2;
+
+  extensions 1001;  // REDACTED
+  optional NextPageToken next_page_token = 1002;
+  extensions 1003;  // InPlaceUpdateToken
+
+  reserved 1, 194964015;
+}
diff --git a/chromium/components/feed/core/proto/v2/wire/version.proto b/chromium/components/feed/core/proto/v2/wire/version.proto
new file mode 100644
index 00000000000..6ead96a0f5c
--- /dev/null
+++ b/chromium/components/feed/core/proto/v2/wire/version.proto
@@ -0,0 +1,44 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+syntax = "proto2";
+
+package feedwire;
+
+option optimize_for = LITE_RUNTIME;
+
+// Specification of an application or OS version.
+// A version string typically looks like: 'major.minor.build.revision'
+message Version {
+  optional int32 major = 1;
+  optional int32 minor = 2;
+  optional int32 build = 3;
+  optional int32 revision = 4;
+
+  // The CPU architecture that the native libraries support
+  enum Architecture {
+    UNKNOWN_ARCHITECTURE = 0;
+    ARM = 1;
+    ARM64 = 2;
+    MIPS = 3;
+    MIPS64 = 4;
+    X86 = 5;
+    X86_64 = 6;
+  }
+  optional Architecture architecture = 5;
+
+  // The release stage of the build
+  enum BuildType {
+    UNKNOWN_BUILD_TYPE = 0;
+    DEV = 1;
+    ALPHA = 2;
+    BETA = 3;
+    RELEASE = 4;
+  }
+  optional BuildType build_type = 6;
+
+  // Specific to Android OS versions. Specifies the API version that the OS
+  // supports.
+  optional int32 api_version = 7;
+}
diff --git a/chromium/components/feed/core/proto/wire/action_payload.proto b/chromium/components/feed/core/proto/wire/action_payload.proto
index e7923e73590..96c49df59ae 100644
--- a/chromium/components/feed/core/proto/wire/action_payload.proto
+++ b/chromium/components/feed/core/proto/wire/action_payload.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/action_payload_for_test.proto b/chromium/components/feed/core/proto/wire/action_payload_for_test.proto
index b382bc1c02d..0eef9277501 100644
--- a/chromium/components/feed/core/proto/wire/action_payload_for_test.proto
+++ b/chromium/components/feed/core/proto/wire/action_payload_for_test.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
@@ -19,7 +19,7 @@ message ActionPayloadForTest {
   // The mid that represents the topic of the story on the card
   optional string id = 1;
 
-  extend components.feed.core.proto.wire.ActionPayload {
+  extend feedwire1.ActionPayload {
     optional ActionPayloadForTest action_payload_for_test_extension = 2;
   }
 }
diff --git a/chromium/components/feed/core/proto/wire/action_request.proto b/chromium/components/feed/core/proto/wire/action_request.proto
index 5e47d7ead47..78b000bb1f1 100644
--- a/chromium/components/feed/core/proto/wire/action_request.proto
+++ b/chromium/components/feed/core/proto/wire/action_request.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/action_type.proto b/chromium/components/feed/core/proto/wire/action_type.proto
index efc1ddf85df..f0e8fd69e7a 100644
--- a/chromium/components/feed/core/proto/wire/action_type.proto
+++ b/chromium/components/feed/core/proto/wire/action_type.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/capability.proto b/chromium/components/feed/core/proto/wire/capability.proto
index 512206469af..6bfb7860787 100644
--- a/chromium/components/feed/core/proto/wire/capability.proto
+++ b/chromium/components/feed/core/proto/wire/capability.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
@@ -12,7 +12,7 @@ option java_package = "org.chromium.components.feed.core.proto.wire";
 option java_outer_classname = "CapabilityProto";
 
 // Feature capability of either the client or the server.
-// Next ID: 12.
+// Next ID: 14.
 enum Capability {
   UNKNOWN_CAPABILITY = 0;
   BASE_UI = 1;
@@ -24,7 +24,8 @@ enum Capability {
   ARTICLE_SNIPPETS = 8;
   CAROUSELS = 9;
   ELEMENTS = 10;
-  CONTENT_ID_UNIFICATION = 11;
+  SEND_FEEDBACK = 12;
+  CLICK_ACTION = 13;
 
-  reserved 3;
+  reserved 3, 11;
 }
diff --git a/chromium/components/feed/core/proto/wire/client_info.proto b/chromium/components/feed/core/proto/wire/client_info.proto
index 4138682452e..c395cca3df9 100644
--- a/chromium/components/feed/core/proto/wire/client_info.proto
+++ b/chromium/components/feed/core/proto/wire/client_info.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/consistency_token.proto b/chromium/components/feed/core/proto/wire/consistency_token.proto
index f172b364bb2..4b7b209d942 100644
--- a/chromium/components/feed/core/proto/wire/consistency_token.proto
+++ b/chromium/components/feed/core/proto/wire/consistency_token.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/content_id.proto b/chromium/components/feed/core/proto/wire/content_id.proto
index f35d86518c7..51ba3334a71 100644
--- a/chromium/components/feed/core/proto/wire/content_id.proto
+++ b/chromium/components/feed/core/proto/wire/content_id.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/data_operation.proto b/chromium/components/feed/core/proto/wire/data_operation.proto
index bc7f178b8a4..a917619b2c0 100644
--- a/chromium/components/feed/core/proto/wire/data_operation.proto
+++ b/chromium/components/feed/core/proto/wire/data_operation.proto
@@ -8,7 +8,7 @@ import "components/feed/core/proto/wire/feature.proto";
 import "components/feed/core/proto/wire/payload_metadata.proto";
 import "components/feed/core/proto/ui/piet/piet.proto";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/display_info.proto b/chromium/components/feed/core/proto/wire/display_info.proto
index ba2bd6b3434..7d0a2dbc262 100644
--- a/chromium/components/feed/core/proto/wire/display_info.proto
+++ b/chromium/components/feed/core/proto/wire/display_info.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feature.proto b/chromium/components/feed/core/proto/wire/feature.proto
index 9f0c4c01739..24741223b8e 100644
--- a/chromium/components/feed/core/proto/wire/feature.proto
+++ b/chromium/components/feed/core/proto/wire/feature.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_action.proto b/chromium/components/feed/core/proto/wire/feed_action.proto
index 8b04bc8ab45..dce68844591 100644
--- a/chromium/components/feed/core/proto/wire/feed_action.proto
+++ b/chromium/components/feed/core/proto/wire/feed_action.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_action_query_data.proto b/chromium/components/feed/core/proto/wire/feed_action_query_data.proto
index ce228c1168f..46cd59cf823 100644
--- a/chromium/components/feed/core/proto/wire/feed_action_query_data.proto
+++ b/chromium/components/feed/core/proto/wire/feed_action_query_data.proto
@@ -7,7 +7,7 @@ syntax = "proto2";
 import "components/feed/core/proto/wire/action_type.proto";
 import "components/feed/core/proto/wire/semantic_properties.proto";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_action_request.proto b/chromium/components/feed/core/proto/wire/feed_action_request.proto
index 72fda0e2f41..a82e7ceb962 100644
--- a/chromium/components/feed/core/proto/wire/feed_action_request.proto
+++ b/chromium/components/feed/core/proto/wire/feed_action_request.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_action_response.proto b/chromium/components/feed/core/proto/wire/feed_action_response.proto
index 5ea0e391738..4e201632451 100644
--- a/chromium/components/feed/core/proto/wire/feed_action_response.proto
+++ b/chromium/components/feed/core/proto/wire/feed_action_response.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_query.proto b/chromium/components/feed/core/proto/wire/feed_query.proto
index 76a94142ec7..2620819c328 100644
--- a/chromium/components/feed/core/proto/wire/feed_query.proto
+++ b/chromium/components/feed/core/proto/wire/feed_query.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_request.proto b/chromium/components/feed/core/proto/wire/feed_request.proto
index 162b640c604..b67a006d69f 100644
--- a/chromium/components/feed/core/proto/wire/feed_request.proto
+++ b/chromium/components/feed/core/proto/wire/feed_request.proto
@@ -11,7 +11,7 @@ import "components/feed/core/proto/wire/feed_action_query_data.proto";
 import "components/feed/core/proto/wire/feed_query.proto";
 import "components/feed/core/proto/wire/request.proto";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/feed_response.proto b/chromium/components/feed/core/proto/wire/feed_response.proto
index 74578002de4..ec101483f8b 100644
--- a/chromium/components/feed/core/proto/wire/feed_response.proto
+++ b/chromium/components/feed/core/proto/wire/feed_response.proto
@@ -8,7 +8,7 @@ import "components/feed/core/proto/wire/capability.proto";
 import "components/feed/core/proto/wire/data_operation.proto";
 import "components/feed/core/proto/wire/response.proto";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/mockserver/mock_server.proto b/chromium/components/feed/core/proto/wire/mockserver/mock_server.proto
index 67a2c39f240..7fc41e4f923 100644
--- a/chromium/components/feed/core/proto/wire/mockserver/mock_server.proto
+++ b/chromium/components/feed/core/proto/wire/mockserver/mock_server.proto
@@ -14,7 +14,7 @@ option java_outer_classname = "MockServerProto";
 
 message MockServer {
   // The initial response
-  optional components.feed.core.proto.wire.Response initial_response = 1;
+  optional feedwire1.Response initial_response = 1;
 
   // conditional responses represent responses for paged content
   repeated ConditionalResponse conditional_responses = 2;
@@ -25,7 +25,7 @@ message MockServer {
 /** This represents a response providing updates to the stream. */
 message MockUpdate {
   // The response with the push update
-  optional components.feed.core.proto.wire.Response response = 1;
+  optional feedwire1.Response response = 1;
 
   // The amount of time to wait, in milliseconds, before the push is triggered.
   // This is relative to the time the GCL file is loaded.
@@ -38,5 +38,5 @@ message ConditionalResponse {
   optional bytes continuation_token = 1;
 
   // The response to use
-  optional components.feed.core.proto.wire.Response response = 2;
+  optional feedwire1.Response response = 2;
 }
diff --git a/chromium/components/feed/core/proto/wire/payload_metadata.proto b/chromium/components/feed/core/proto/wire/payload_metadata.proto
index e40e0c4c252..d695087a05e 100644
--- a/chromium/components/feed/core/proto/wire/payload_metadata.proto
+++ b/chromium/components/feed/core/proto/wire/payload_metadata.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/piet_shared_state_item.proto b/chromium/components/feed/core/proto/wire/piet_shared_state_item.proto
index c57a47cfcff..99f4d420998 100644
--- a/chromium/components/feed/core/proto/wire/piet_shared_state_item.proto
+++ b/chromium/components/feed/core/proto/wire/piet_shared_state_item.proto
@@ -7,7 +7,7 @@ syntax = "proto2";
 import "components/feed/core/proto/ui/piet/piet.proto";
 import "components/feed/core/proto/wire/content_id.proto";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/request.proto b/chromium/components/feed/core/proto/wire/request.proto
index d26e8089eba..a02372025b1 100644
--- a/chromium/components/feed/core/proto/wire/request.proto
+++ b/chromium/components/feed/core/proto/wire/request.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/response.proto b/chromium/components/feed/core/proto/wire/response.proto
index 81e4f2658bf..11692309e9e 100644
--- a/chromium/components/feed/core/proto/wire/response.proto
+++ b/chromium/components/feed/core/proto/wire/response.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/semantic_properties.proto b/chromium/components/feed/core/proto/wire/semantic_properties.proto
index c6327b8c777..d478b7744a5 100644
--- a/chromium/components/feed/core/proto/wire/semantic_properties.proto
+++ b/chromium/components/feed/core/proto/wire/semantic_properties.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/proto/wire/token.proto b/chromium/components/feed/core/proto/wire/token.proto
index 8cdb8770e8a..e14edf2f643 100644
--- a/chromium/components/feed/core/proto/wire/token.proto
+++ b/chromium/components/feed/core/proto/wire/token.proto
@@ -6,7 +6,7 @@ syntax = "proto2";
 
 import "components/feed/core/proto/wire/feature.proto";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
@@ -15,9 +15,7 @@ option java_outer_classname = "TokenProto";
 
 // A continuation token (paging token).
 message Token {
-  extend components.feed.core.proto.wire.Feature {
-    optional Token token_extension = 194964015;
-  }
+  extend feedwire1.Feature { optional Token token_extension = 194964015; }
 
   // Indicates the last position of the current content for a parent.  A request
   // can be made using the next_page_token to get additional features which will
diff --git a/chromium/components/feed/core/proto/wire/version.proto b/chromium/components/feed/core/proto/wire/version.proto
index 164753b7fe8..ba9ef172eef 100644
--- a/chromium/components/feed/core/proto/wire/version.proto
+++ b/chromium/components/feed/core/proto/wire/version.proto
@@ -4,7 +4,7 @@
 
 syntax = "proto2";
 
-package components.feed.core.proto.wire;
+package feedwire1;
 
 option optimize_for = LITE_RUNTIME;
 
diff --git a/chromium/components/feed/core/shared_prefs/BUILD.gn b/chromium/components/feed/core/shared_prefs/BUILD.gn
new file mode 100644
index 00000000000..9b0b637fc77
--- /dev/null
+++ b/chromium/components/feed/core/shared_prefs/BUILD.gn
@@ -0,0 +1,12 @@
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+static_library("feed_shared_prefs") {
+  sources = [
+    "pref_names.cc",
+    "pref_names.h",
+  ]
+
+  deps = [ "//components/prefs" ]
+}
diff --git a/chromium/components/feed/core/shared_prefs/pref_names.cc b/chromium/components/feed/core/shared_prefs/pref_names.cc
new file mode 100644
index 00000000000..da75d63d4c4
--- /dev/null
+++ b/chromium/components/feed/core/shared_prefs/pref_names.cc
@@ -0,0 +1,26 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_SHARED_PREFS_PREF_NAMES_CC_
+#define COMPONENTS_FEED_CORE_SHARED_PREFS_PREF_NAMES_CC_
+
+#include "components/feed/core/shared_prefs/pref_names.h"
+
+#include "components/prefs/pref_registry_simple.h"
+
+namespace feed {
+namespace prefs {
+
+const char kEnableSnippets[] = "ntp_snippets.enable";
+const char kArticlesListVisible[] = "ntp_snippets.list_visible";
+
+void RegisterFeedSharedProfilePrefs(PrefRegistrySimple* registry) {
+  registry->RegisterBooleanPref(kEnableSnippets, true);
+  registry->RegisterBooleanPref(kArticlesListVisible, true);
+}
+
+}  // namespace prefs
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_SHARED_PREFS_PREF_NAMES_CC_
diff --git a/chromium/components/feed/core/shared_prefs/pref_names.h b/chromium/components/feed/core/shared_prefs/pref_names.h
new file mode 100644
index 00000000000..27fa5e3f65b
--- /dev/null
+++ b/chromium/components/feed/core/shared_prefs/pref_names.h
@@ -0,0 +1,27 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_SHARED_PREFS_PREF_NAMES_H_
+#define COMPONENTS_FEED_CORE_SHARED_PREFS_PREF_NAMES_H_
+
+class PrefRegistrySimple;
+
+// These prefs are shared by Feed and Zine (ntp_snippets).
+
+namespace feed {
+namespace prefs {
+
+// If set to false, remote suggestions are completely disabled. This is set by
+// an enterprise policy.
+extern const char kEnableSnippets[];
+
+// Whether the list of NTP snippets is visible in UI. This is set to false when
+// the user toggles the list off.
+extern const char kArticlesListVisible[];
+
+void RegisterFeedSharedProfilePrefs(PrefRegistrySimple* registry);
+}  // namespace prefs
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_SHARED_PREFS_PREF_NAMES_H_
diff --git a/chromium/components/feed/core/v2/BUILD.gn b/chromium/components/feed/core/v2/BUILD.gn
new file mode 100644
index 00000000000..99d8d69a7c1
--- /dev/null
+++ b/chromium/components/feed/core/v2/BUILD.gn
@@ -0,0 +1,117 @@
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//testing/test.gni")
+
+if (is_android) {
+  import("//build/config/android/rules.gni")
+}
+
+source_set("feed_core_v2") {
+  sources = [
+    "enums.cc",
+    "enums.h",
+    "feed_network.cc",
+    "feed_network.h",
+    "feed_network_impl.cc",
+    "feed_network_impl.h",
+    "feed_store.cc",
+    "feed_store.h",
+    "feed_stream.cc",
+    "feed_stream.h",
+    "prefs.cc",
+    "prefs.h",
+    "proto_util.cc",
+    "proto_util.h",
+    "public/feed_service.cc",
+    "public/feed_service.h",
+    "public/feed_stream_api.h",
+    "refresh_task_scheduler.h",
+    "request_throttler.cc",
+    "request_throttler.h",
+    "scheduling.cc",
+    "scheduling.h",
+    "stream_event_metrics.cc",
+    "stream_event_metrics.h",
+    "stream_model.cc",
+    "stream_model.h",
+    "stream_model/ephemeral_change.cc",
+    "stream_model/ephemeral_change.h",
+    "stream_model/feature_tree.cc",
+    "stream_model/feature_tree.h",
+    "stream_model_update_request.cc",
+    "stream_model_update_request.h",
+    "tasks/load_stream_from_store_task.cc",
+    "tasks/load_stream_from_store_task.h",
+    "tasks/load_stream_task.cc",
+    "tasks/load_stream_task.h",
+    "tasks/wait_for_store_initialize_task.cc",
+    "tasks/wait_for_store_initialize_task.h",
+  ]
+  deps = [
+    "//components/feed/core:feed_core",
+    "//components/feed/core/common:feed_core_common",
+    "//components/offline_pages/task:task",
+    "//components/prefs",
+    "//components/signin/public/identity_manager",
+    "//components/variations",
+    "//components/variations/net",
+    "//components/web_resource:web_resource",
+    "//net",
+    "//services/network/public/cpp",
+    "//services/network/public/mojom",
+    "//third_party/zlib/google:compression_utils",
+  ]
+
+  public_deps = [
+    "//base",
+    "//components/feed/core/common:feed_core_common",
+    "//components/feed/core/proto:proto_v2",
+  ]
+}
+
+source_set("core_unit_tests") {
+  testonly = true
+  sources = [
+    "feed_network_impl_unittest.cc",
+    "feed_store_unittest.cc",
+    "feed_stream_unittest.cc",
+    "request_throttler_unittest.cc",
+    "stream_model_unittest.cc",
+    "stream_model_update_request_unittest.cc",
+    "test/callback_receiver.h",
+    "test/callback_receiver.h",
+    "test/proto_printer.cc",
+    "test/proto_printer.h",
+    "test/stream_builder.cc",
+    "test/stream_builder.h",
+  ]
+
+  deps = [
+    ":feed_core_v2",
+    ":unit_tests_bundle_data",
+    "//base",
+    "//base/test:test_support",
+    "//components/feed/core:feed_core",
+    "//components/feed/core/common:feed_core_common",
+    "//components/leveldb_proto:test_support",
+    "//components/prefs:test_support",
+    "//components/signin/public/identity_manager",
+    "//components/signin/public/identity_manager:test_support",
+    "//net:test_support",
+    "//services/network:test_support",
+    "//services/network/public/cpp",
+    "//services/network/public/mojom",
+    "//testing/gtest",
+    "//third_party/zlib/google:compression_utils",
+  ]
+}
+
+bundle_data("unit_tests_bundle_data") {
+  visibility = [ ":core_unit_tests" ]
+  testonly = true
+  sources = [ "//components/test/data/feed/response.binarypb" ]
+  outputs = [ "{{bundle_resources_dir}}/" +
+              "{{source_root_relative_dir}}/{{source_file_part}}" ]
+}
diff --git a/chromium/components/feed/core/v2/README.md b/chromium/components/feed/core/v2/README.md
new file mode 100644
index 00000000000..267bc51312b
--- /dev/null
+++ b/chromium/components/feed/core/v2/README.md
@@ -0,0 +1 @@
+The next iteration of the feed component, in development.
diff --git a/chromium/components/feed/core/v2/enums.cc b/chromium/components/feed/core/v2/enums.cc
new file mode 100644
index 00000000000..ce8c0ce37ec
--- /dev/null
+++ b/chromium/components/feed/core/v2/enums.cc
@@ -0,0 +1,52 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/enums.h"
+
+#include <ostream>
+
+namespace feed {
+
+// Included for debug builds only for reduced binary size.
+
+std::ostream& operator<<(std::ostream& out, LoadStreamStatus value) {
+#ifndef NDEBUG
+  switch (value) {
+    case LoadStreamStatus::kNoStatus:
+      return out << "kNoStatus";
+    case LoadStreamStatus::kLoadedFromStore:
+      return out << "kLoadedFromStore";
+    case LoadStreamStatus::kLoadedFromNetwork:
+      return out << "kLoadedFromNetwork";
+    case LoadStreamStatus::kFailedWithStoreError:
+      return out << "kFailedWithStoreError";
+    case LoadStreamStatus::kNoStreamDataInStore:
+      return out << "kNoStreamDataInStore";
+    case LoadStreamStatus::kModelAlreadyLoaded:
+      return out << "kModelAlreadyLoaded";
+    case LoadStreamStatus::kNoResponseBody:
+      return out << "kNoResponseBody";
+    case LoadStreamStatus::kProtoTranslationFailed:
+      return out << "kProtoTranslationFailed";
+    case LoadStreamStatus::kDataInStoreIsStale:
+      return out << "kDataInStoreIsStale";
+    case LoadStreamStatus::kDataInStoreIsStaleTimestampInFuture:
+      return out << "kDataInStoreIsStaleTimestampInFuture";
+    case LoadStreamStatus::kCannotLoadFromNetworkSupressedForHistoryDelete:
+      return out << "kCannotLoadFromNetworkSupressedForHistoryDelete";
+    case LoadStreamStatus::kCannotLoadFromNetworkOffline:
+      return out << "kCannotLoadFromNetworkOffline";
+    case LoadStreamStatus::kCannotLoadFromNetworkThrottled:
+      return out << "kCannotLoadFromNetworkThrottled";
+    case LoadStreamStatus::kLoadNotAllowedEulaNotAccepted:
+      return out << "kLoadNotAllowedEulaNotAccepted";
+    case LoadStreamStatus::kLoadNotAllowedArticlesListHidden:
+      return out << "kLoadNotAllowedArticlesListHidden";
+  }
+#else
+  return out << (static_cast<int>(value));
+#endif  // ifndef NDEBUG
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/enums.h b/chromium/components/feed/core/v2/enums.h
new file mode 100644
index 00000000000..dc6d84e2e96
--- /dev/null
+++ b/chromium/components/feed/core/v2/enums.h
@@ -0,0 +1,45 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_ENUMS_H_
+#define COMPONENTS_FEED_CORE_V2_ENUMS_H_
+
+#include <iosfwd>
+
+#include "components/feed/core/common/enums.h"
+
+namespace feed {
+
+enum NetworkRequestType : int {
+  kFeedQuery = 0,
+  kUploadActions = 1,
+};
+
+enum class LoadStreamStatus {
+  // Loading was not attempted.
+  kNoStatus = 0,
+  kLoadedFromStore = 1,
+  kLoadedFromNetwork = 2,
+  kFailedWithStoreError = 3,
+  kNoStreamDataInStore = 4,
+  kModelAlreadyLoaded = 5,
+  kNoResponseBody = 6,
+  // TODO(harringtond): Let's add more specific proto translation errors.
+  kProtoTranslationFailed = 7,
+  kDataInStoreIsStale = 8,
+  // The timestamp for stored data is in the future, so we're treating stored
+  // data as it it is stale.
+  kDataInStoreIsStaleTimestampInFuture = 9,
+  kCannotLoadFromNetworkSupressedForHistoryDelete = 10,
+  kCannotLoadFromNetworkOffline = 11,
+  kCannotLoadFromNetworkThrottled = 12,
+  kLoadNotAllowedEulaNotAccepted = 13,
+  kLoadNotAllowedArticlesListHidden = 14,
+};
+
+std::ostream& operator<<(std::ostream& out, LoadStreamStatus value);
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_ENUMS_H_
diff --git a/chromium/components/feed/core/v2/feed_network.cc b/chromium/components/feed/core/v2/feed_network.cc
new file mode 100644
index 00000000000..5bca7bf3bba
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_network.cc
@@ -0,0 +1,30 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_network.h"
+
+#include "components/feed/core/proto/v2/wire/action_request.pb.h"
+#include "components/feed/core/proto/v2/wire/feed_action_response.pb.h"
+#include "components/feed/core/proto/v2/wire/request.pb.h"
+#include "components/feed/core/proto/v2/wire/response.pb.h"
+
+namespace feed {
+
+FeedNetwork::QueryRequestResult::QueryRequestResult() = default;
+FeedNetwork::QueryRequestResult::~QueryRequestResult() = default;
+FeedNetwork::QueryRequestResult::QueryRequestResult(QueryRequestResult&&) =
+    default;
+FeedNetwork::QueryRequestResult& FeedNetwork::QueryRequestResult::operator=(
+    QueryRequestResult&&) = default;
+
+FeedNetwork::ActionRequestResult::ActionRequestResult() = default;
+FeedNetwork::ActionRequestResult::~ActionRequestResult() = default;
+FeedNetwork::ActionRequestResult::ActionRequestResult(ActionRequestResult&&) =
+    default;
+FeedNetwork::ActionRequestResult& FeedNetwork::ActionRequestResult::operator=(
+    ActionRequestResult&&) = default;
+
+FeedNetwork::~FeedNetwork() = default;
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/feed_network.h b/chromium/components/feed/core/v2/feed_network.h
new file mode 100644
index 00000000000..8a25a238117
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_network.h
@@ -0,0 +1,69 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_FEED_NETWORK_H_
+#define COMPONENTS_FEED_CORE_V2_FEED_NETWORK_H_
+
+#include <memory>
+#include "base/callback.h"
+
+namespace feedwire {
+class ActionRequest;
+class FeedActionResponse;
+class Request;
+class Response;
+}  // namespace feedwire
+
+namespace feed {
+
+class FeedNetwork {
+ public:
+  // Result of SendQueryRequest.
+  struct QueryRequestResult {
+    QueryRequestResult();
+    ~QueryRequestResult();
+    QueryRequestResult(QueryRequestResult&&);
+    QueryRequestResult& operator=(QueryRequestResult&&);
+    // HTTP status code if one was received, 0 otherwise.
+    int32_t status_code = 0;
+    // Response body if one was received.
+    std::unique_ptr<feedwire::Response> response_body;
+  };
+
+  // Result of SendActionRequest.
+  struct ActionRequestResult {
+    ActionRequestResult();
+    ~ActionRequestResult();
+    ActionRequestResult(ActionRequestResult&&);
+    ActionRequestResult& operator=(ActionRequestResult&&);
+    // HTTP status code if one was received, 0 otherwise.
+    int32_t status_code = 0;
+    // Response body if one was received.
+    std::unique_ptr<feedwire::FeedActionResponse> response_body;
+  };
+
+  virtual ~FeedNetwork();
+
+  // Send a feedwire::Request, and receive the response in |callback|.
+  // |callback| will be called unless the request is canceled with
+  // |CancelRequests()|.
+  virtual void SendQueryRequest(
+      const feedwire::Request& request,
+      base::OnceCallback<void(QueryRequestResult)> callback) = 0;
+
+  // Send a feedwire::ActionRequest, and receive the response in |callback|.
+  // |callback| will be called unless the request is canceled with
+  // |CancelRequests()|.
+  virtual void SendActionRequest(
+      const feedwire::ActionRequest& request,
+      base::OnceCallback<void(ActionRequestResult)> callback) = 0;
+
+  // Cancels all pending requests immediately. This could be used, for example,
+  // if there are pending requests for a user who just signed out.
+  virtual void CancelRequests() = 0;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_FEED_NETWORK_H_
diff --git a/chromium/components/feed/core/v2/feed_network_impl.cc b/chromium/components/feed/core/v2/feed_network_impl.cc
new file mode 100644
index 00000000000..5231a84277f
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_network_impl.cc
@@ -0,0 +1,458 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_network_impl.h"
+#include "base/bind.h"
+#include "base/containers/flat_set.h"
+#include "base/metrics/histogram_functions.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/time/tick_clock.h"
+#include "base/time/time.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/proto/v2/wire/action_request.pb.h"
+#include "components/feed/core/proto/v2/wire/feed_action_response.pb.h"
+#include "components/feed/core/proto/v2/wire/feed_query.pb.h"
+#include "components/feed/core/proto/v2/wire/request.pb.h"
+#include "components/feed/core/proto/v2/wire/response.pb.h"
+#include "components/prefs/pref_service.h"
+#include "components/signin/public/identity_manager/access_token_info.h"
+#include "components/signin/public/identity_manager/identity_manager.h"
+#include "components/signin/public/identity_manager/primary_account_access_token_fetcher.h"
+#include "components/signin/public/identity_manager/scope_set.h"
+#include "components/variations/net/variations_http_headers.h"
+#include "net/base/load_flags.h"
+#include "net/base/url_util.h"
+#include "net/http/http_response_headers.h"
+#include "net/http/http_status_code.h"
+#include "net/traffic_annotation/network_traffic_annotation.h"
+#include "services/network/public/cpp/resource_request.h"
+#include "services/network/public/cpp/resource_request_body.h"
+#include "services/network/public/cpp/shared_url_loader_factory.h"
+#include "services/network/public/cpp/simple_url_loader.h"
+#include "third_party/zlib/google/compression_utils.h"
+
+namespace feed {
+namespace {
+constexpr char kAuthenticationScope[] =
+    "https://www.googleapis.com/auth/googlenow";
+constexpr char kApplicationOctetStream[] = "application/octet-stream";
+constexpr base::TimeDelta kNetworkTimeout = base::TimeDelta::FromSeconds(30);
+
+constexpr char kFeedQueryUrl[] =
+    "https://www.google.com/httpservice/retry/InteractiveDiscoverAgaService/"
+    "FeedQuery";
+constexpr char kNextPageQueryUrl[] =
+    "https://www.google.com/httpservice/retry/InteractiveDiscoverAgaService/"
+    "NextPageQuery";
+constexpr char kBackgroundQueryUrl[] =
+    "https://www.google.com/httpservice/noretry/BackgroundDiscoverAgaService/"
+    "FeedQuery";
+
+using RawResponse = FeedNetworkImpl::RawResponse;
+}  // namespace
+
+struct FeedNetworkImpl::RawResponse {
+  // A union of net::Error (if the request failed) and the http
+  // status code(if the request succeeded in reaching the server).
+  int32_t status_code;
+  // HTTP response body.
+  std::string response_bytes;
+};
+
+namespace {
+template <typename RESULT>
+void ParseAndForwardResponse(base::OnceCallback<void(RESULT)> result_callback,
+                             RawResponse raw_response) {
+  RESULT result;
+  result.status_code = raw_response.status_code;
+  if (result.status_code == 200) {
+    auto response_message = std::make_unique<typename decltype(
+        result.response_body)::element_type>();
+    if (response_message->ParseFromString(raw_response.response_bytes)) {
+      result.response_body = std::move(response_message);
+    }
+  }
+  std::move(result_callback).Run(std::move(result));
+}
+
+void AddMothershipPayloadQueryParams(bool is_post,
+                                     const std::string& payload,
+                                     const std::string& language_tag,
+                                     GURL* url) {
+  if (!is_post)
+    *url = net::AppendQueryParameter(*url, "reqpld", payload);
+  *url = net::AppendQueryParameter(*url, "fmt", "bin");
+  if (!language_tag.empty())
+    *url = net::AppendQueryParameter(*url, "hl", language_tag);
+}
+
+}  // namespace
+
+// Each NetworkFetch instance represents a single "logical" fetch that ends by
+// calling the associated callback. Network fetches will actually attempt two
+// fetches if there is a signed in user; the first to retrieve an access token,
+// and the second to the specified url.
+class FeedNetworkImpl::NetworkFetch {
+ public:
+  NetworkFetch(const GURL& url,
+               const std::string& request_type,
+               std::string request_body,
+               signin::IdentityManager* identity_manager,
+               network::SharedURLLoaderFactory* loader_factory,
+               const std::string& api_key,
+               const base::TickClock* tick_clock,
+               PrefService* pref_service)
+      : url_(url),
+        request_type_(request_type),
+        request_body_(std::move(request_body)),
+        identity_manager_(identity_manager),
+        loader_factory_(loader_factory),
+        api_key_(api_key),
+        tick_clock_(tick_clock),
+        entire_send_start_ticks_(tick_clock_->NowTicks()),
+        pref_service_(pref_service) {
+    // Apply the host override (from snippets-internals).
+    std::string host_override =
+        pref_service_->GetString(feed::prefs::kHostOverrideHost);
+    if (!host_override.empty()) {
+      GURL override_host_url(host_override);
+      if (override_host_url.is_valid()) {
+        GURL::Replacements replacements;
+        replacements.SetSchemeStr(override_host_url.scheme_piece());
+        replacements.SetHostStr(override_host_url.host_piece());
+        replacements.SetPortStr(override_host_url.port_piece());
+        url_ = url_.ReplaceComponents(replacements);
+        host_overridden_ = true;
+      }
+    }
+  }
+  ~NetworkFetch() = default;
+  NetworkFetch(const NetworkFetch&) = delete;
+  NetworkFetch& operator=(const NetworkFetch&) = delete;
+
+  void Start(base::OnceCallback<void(RawResponse)> done_callback) {
+    done_callback_ = std::move(done_callback);
+
+    if (!identity_manager_->HasPrimaryAccount()) {
+      StartLoader();
+      return;
+    }
+
+    StartAccessTokenFetch();
+  }
+
+ private:
+  void StartAccessTokenFetch() {
+    signin::ScopeSet scopes{kAuthenticationScope};
+    // It's safe to pass base::Unretained(this) since deleting the token fetcher
+    // will prevent the callback from being completed.
+    token_fetcher_ = std::make_unique<signin::PrimaryAccountAccessTokenFetcher>(
+        "feed", identity_manager_, scopes,
+        base::BindOnce(&NetworkFetch::AccessTokenFetchFinished,
+                       base::Unretained(this), tick_clock_->NowTicks()),
+        signin::PrimaryAccountAccessTokenFetcher::Mode::kWaitUntilAvailable);
+  }
+
+  void AccessTokenFetchFinished(base::TimeTicks token_start_ticks,
+                                GoogleServiceAuthError error,
+                                signin::AccessTokenInfo access_token_info) {
+    UMA_HISTOGRAM_ENUMERATION(
+        "ContentSuggestions.Feed.Network.TokenFetchStatus", error.state(),
+        GoogleServiceAuthError::NUM_STATES);
+
+    base::TimeDelta token_duration =
+        tick_clock_->NowTicks() - token_start_ticks;
+    UMA_HISTOGRAM_MEDIUM_TIMES("ContentSuggestions.Feed.Network.TokenDuration",
+                               token_duration);
+
+    access_token_ = access_token_info.token;
+    StartLoader();
+  }
+
+  void StartLoader() {
+    loader_only_start_ticks_ = tick_clock_->NowTicks();
+    simple_loader_ = MakeLoader();
+    simple_loader_->DownloadToStringOfUnboundedSizeUntilCrashAndDie(
+        loader_factory_, base::BindOnce(&NetworkFetch::OnSimpleLoaderComplete,
+                                        base::Unretained(this)));
+  }
+
+  std::unique_ptr<network::SimpleURLLoader> MakeLoader() {
+    // TODO(pnoland): Add data use measurement once it's supported for simple
+    // url loader.
+    net::NetworkTrafficAnnotationTag traffic_annotation =
+        net::DefineNetworkTrafficAnnotation("interest_feedv2_send", R"(
+        semantics {
+          sender: "Feed Library"
+          description: "Chrome can show content suggestions (e.g. articles) "
+            "in the form of a feed. For signed-in users, these may be "
+            "personalized based on interest signals in the user's account."
+          trigger: "Triggered periodically in the background, or upon "
+            "explicit user request."
+          data: "The locale of the device and data describing the suggested "
+            "content that the user interacted with. For signed-in users "
+            "the request is authenticated. "
+          destination: GOOGLE_OWNED_SERVICE
+        }
+        policy {
+          cookies_allowed: YES
+          cookies_store: "user"
+          setting: "This can be disabled from the New Tab Page by collapsing "
+          "the articles section."
+          chrome_policy {
+            NTPContentSuggestionsEnabled {
+              policy_options {mode: MANDATORY}
+              NTPContentSuggestionsEnabled: false
+            }
+          }
+        })");
+    GURL url(url_);
+    if (access_token_.empty() && !api_key_.empty())
+      url = net::AppendQueryParameter(url_, "key", api_key_);
+
+    auto resource_request = std::make_unique<network::ResourceRequest>();
+    resource_request->url = url;
+
+    resource_request->load_flags = net::LOAD_BYPASS_CACHE;
+    resource_request->credentials_mode = network::mojom::CredentialsMode::kOmit;
+    resource_request->method = request_type_;
+
+    // Include credentials ONLY if the user has overridden the feed host through
+    // the internals page. This allows for some authentication workflows we need
+    // for testing.
+    if (host_overridden_) {
+      resource_request->credentials_mode =
+          network::mojom::CredentialsMode::kInclude;
+      resource_request->site_for_cookies = net::SiteForCookies::FromUrl(url);
+    }
+
+    SetRequestHeaders(!request_body_.empty(), resource_request.get());
+
+    auto simple_loader = network::SimpleURLLoader::Create(
+        std::move(resource_request), traffic_annotation);
+    simple_loader->SetAllowHttpErrorResults(true);
+    simple_loader->SetTimeoutDuration(kNetworkTimeout);
+    PopulateRequestBody(simple_loader.get());
+    return simple_loader;
+  }
+
+  void SetRequestHeaders(bool has_request_body,
+                         network::ResourceRequest* request) const {
+    if (has_request_body) {
+      request->headers.SetHeader(net::HttpRequestHeaders::kContentType,
+                                 kApplicationOctetStream);
+      request->headers.SetHeader("Content-Encoding", "gzip");
+    }
+
+    variations::SignedIn signed_in_status = variations::SignedIn::kNo;
+    if (!access_token_.empty()) {
+      request->headers.SetHeader(net::HttpRequestHeaders::kAuthorization,
+                                 "Bearer " + access_token_);
+      signed_in_status = variations::SignedIn::kYes;
+    }
+
+    // Add X-Client-Data header with experiment IDs from field trials.
+    variations::AppendVariationsHeader(url_, variations::InIncognito::kNo,
+                                       signed_in_status, request);
+  }
+
+  void PopulateRequestBody(network::SimpleURLLoader* loader) {
+    std::string compressed_request_body;
+    if (!request_body_.empty()) {
+      std::string uncompressed_request_body(
+          reinterpret_cast<const char*>(request_body_.data()),
+          request_body_.size());
+
+      compression::GzipCompress(uncompressed_request_body,
+                                &compressed_request_body);
+
+      loader->AttachStringForUpload(compressed_request_body,
+                                    kApplicationOctetStream);
+    }
+
+    UMA_HISTOGRAM_COUNTS_1M(
+        "ContentSuggestions.Feed.Network.RequestSizeKB.Compressed",
+        static_cast<int>(compressed_request_body.size() / 1024));
+  }
+
+  void OnSimpleLoaderComplete(std::unique_ptr<std::string> response) {
+    int32_t status_code = simple_loader_->NetError();
+    // If overriding the feed host, try to grab the Bless nonce. This is
+    // strictly informational, and only displayed in snippets-internals.
+    if (host_overridden_ && simple_loader_->ResponseInfo()) {
+      size_t iter = 0;
+      std::string value;
+      while (simple_loader_->ResponseInfo()->headers->EnumerateHeader(
+          &iter, "www-authenticate", &value)) {
+        size_t pos = value.find("nonce=\"");
+        if (pos != std::string::npos) {
+          std::string nonce = value.substr(pos + 7, 16);
+          if (nonce.size() == 16) {
+            pref_service_->SetString(feed::prefs::kHostOverrideBlessNonce,
+                                     nonce);
+            break;
+          }
+        }
+      }
+    }
+
+    std::string response_body;
+    if (response) {
+      status_code = simple_loader_->ResponseInfo()->headers->response_code();
+      response_body = std::move(*response);
+
+      if (status_code == net::HTTP_UNAUTHORIZED) {
+        signin::ScopeSet scopes{kAuthenticationScope};
+        CoreAccountId account_id = identity_manager_->GetPrimaryAccountId();
+        if (!account_id.empty()) {
+          identity_manager_->RemoveAccessTokenFromCache(account_id, scopes,
+                                                        access_token_);
+        }
+      }
+    }
+
+    base::TimeDelta entire_send_duration =
+        tick_clock_->NowTicks() - entire_send_start_ticks_;
+    UMA_HISTOGRAM_MEDIUM_TIMES("ContentSuggestions.Feed.Network.Duration",
+                               entire_send_duration);
+
+    base::TimeDelta loader_only_duration =
+        tick_clock_->NowTicks() - loader_only_start_ticks_;
+    // This histogram purposefully matches name and bucket size used in
+    // RemoteSuggestionsFetcherImpl.
+    UMA_HISTOGRAM_TIMES("NewTabPage.Snippets.FetchTime", loader_only_duration);
+
+    base::UmaHistogramSparse(
+        "ContentSuggestions.Feed.Network.RequestStatusCode", status_code);
+
+    // The below is true even if there is a protocol error, so this will
+    // record response size as long as the request completed.
+    if (status_code >= 200) {
+      UMA_HISTOGRAM_COUNTS_1M("ContentSuggestions.Feed.Network.ResponseSizeKB",
+                              static_cast<int>(response_body.size() / 1024));
+    }
+
+    std::move(done_callback_).Run({status_code, std::move(response_body)});
+  }
+
+ private:
+  GURL url_;
+  const std::string request_type_;
+  std::string access_token_;
+  const std::string request_body_;
+  signin::IdentityManager* const identity_manager_;
+  std::unique_ptr<signin::PrimaryAccountAccessTokenFetcher> token_fetcher_;
+  std::unique_ptr<network::SimpleURLLoader> simple_loader_;
+  base::OnceCallback<void(RawResponse)> done_callback_;
+  network::SharedURLLoaderFactory* loader_factory_;
+  const std::string api_key_;
+  const base::TickClock* tick_clock_;
+
+  // Set when the NetworkFetch is constructed, before token and article fetch.
+  const base::TimeTicks entire_send_start_ticks_;
+
+  // Should be set right before the article fetch, and after the token fetch if
+  // there is one.
+  base::TimeTicks loader_only_start_ticks_;
+  PrefService* pref_service_;
+  bool host_overridden_ = false;
+};
+
+FeedNetworkImpl::FeedNetworkImpl(
+    Delegate* delegate,
+    signin::IdentityManager* identity_manager,
+    const std::string& api_key,
+    scoped_refptr<network::SharedURLLoaderFactory> loader_factory,
+    const base::TickClock* tick_clock,
+    PrefService* pref_service)
+    : delegate_(delegate),
+      identity_manager_(identity_manager),
+      api_key_(api_key),
+      loader_factory_(loader_factory),
+      tick_clock_(tick_clock),
+      pref_service_(pref_service) {}
+
+FeedNetworkImpl::~FeedNetworkImpl() = default;
+
+void FeedNetworkImpl::SendQueryRequest(
+    const feedwire::Request& request,
+    base::OnceCallback<void(QueryRequestResult)> callback) {
+  std::string binary_proto;
+  request.SerializeToString(&binary_proto);
+
+  // TODO(harringtond): Decide how we want to override these URLs for testing.
+  // Should probably add a command-line flag.
+  GURL url;
+  switch (request.feed_request().feed_query().reason()) {
+    case feedwire::FeedQuery::SCHEDULED_REFRESH:
+    case feedwire::FeedQuery::IN_PLACE_UPDATE:
+      url = GURL(kBackgroundQueryUrl);
+      break;
+    case feedwire::FeedQuery::NEXT_PAGE_SCROLL:
+      url = GURL(kNextPageQueryUrl);
+      break;
+    case feedwire::FeedQuery::MANUAL_REFRESH:
+      url = GURL(kFeedQueryUrl);
+      break;
+    default:
+      std::move(callback).Run({});
+      return;
+  }
+
+  AddMothershipPayloadQueryParams(/*is_post=*/false, binary_proto,
+                                  delegate_->GetLanguageTag(), &url);
+  Send(url, "GET", /*request_body=*/std::string(),
+       base::BindOnce(&ParseAndForwardResponse<QueryRequestResult>,
+                      std::move(callback)));
+}
+
+void FeedNetworkImpl::SendActionRequest(
+    const feedwire::ActionRequest& request,
+    base::OnceCallback<void(ActionRequestResult)> callback) {
+  std::string binary_proto;
+  request.SerializeToString(&binary_proto);
+
+  GURL url(
+      "https://www.google.com/httpservice/retry/ClankActionUploadService/"
+      "ClankActionUpload");
+  AddMothershipPayloadQueryParams(/*is_post=*/true, /*payload=*/std::string(),
+                                  delegate_->GetLanguageTag(), &url);
+
+  Send(url, "POST", std::move(binary_proto),
+       base::BindOnce(&ParseAndForwardResponse<ActionRequestResult>,
+                      std::move(callback)));
+}
+
+void FeedNetworkImpl::CancelRequests() {
+  pending_requests_.clear();
+}
+
+void FeedNetworkImpl::Send(const GURL& url,
+                           const std::string& request_type,
+                           std::string request_body,
+                           base::OnceCallback<void(RawResponse)> callback) {
+  auto fetch = std::make_unique<NetworkFetch>(
+      url, request_type, std::move(request_body), identity_manager_,
+      loader_factory_.get(), api_key_, tick_clock_, pref_service_);
+  NetworkFetch* fetch_unowned = fetch.get();
+  pending_requests_.emplace(std::move(fetch));
+
+  // It's safe to pass base::Unretained(this) since deleting the network fetch
+  // will prevent the callback from being completed.
+  fetch_unowned->Start(base::BindOnce(&FeedNetworkImpl::SendComplete,
+                                      base::Unretained(this), fetch_unowned,
+                                      std::move(callback)));
+}
+
+void FeedNetworkImpl::SendComplete(
+    NetworkFetch* fetch,
+    base::OnceCallback<void(RawResponse)> callback,
+    RawResponse raw_response) {
+  DCHECK_EQ(1UL, pending_requests_.count(fetch));
+  pending_requests_.erase(fetch);
+
+  std::move(callback).Run(std::move(raw_response));
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/feed_network_impl.h b/chromium/components/feed/core/v2/feed_network_impl.h
new file mode 100644
index 00000000000..b96f25d0b6c
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_network_impl.h
@@ -0,0 +1,91 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_FEED_NETWORK_IMPL_H_
+#define COMPONENTS_FEED_CORE_V2_FEED_NETWORK_IMPL_H_
+
+#include <string>
+#include "base/callback.h"
+#include "base/containers/flat_set.h"
+#include "base/containers/unique_ptr_adapters.h"
+#include "base/memory/scoped_refptr.h"
+#include "components/feed/core/v2/feed_network.h"
+#include "url/gurl.h"
+
+class PrefService;
+namespace base {
+class TickClock;
+}
+namespace signin {
+class IdentityManager;
+}
+namespace network {
+class SharedURLLoaderFactory;
+}
+
+namespace feed {
+
+class FeedNetworkImpl : public FeedNetwork {
+ public:
+  class NetworkFetch;
+  struct RawResponse;
+  class Delegate {
+   public:
+    virtual ~Delegate() = default;
+    // Returns a string which represents the top locale and region of the
+    // device.
+    virtual std::string GetLanguageTag() = 0;
+  };
+
+  FeedNetworkImpl(Delegate* delegate,
+                  signin::IdentityManager* identity_manager,
+                  const std::string& api_key,
+                  scoped_refptr<network::SharedURLLoaderFactory> loader_factory,
+                  const base::TickClock* tick_clock,
+                  PrefService* pref_service);
+  ~FeedNetworkImpl() override;
+  FeedNetworkImpl(const FeedNetworkImpl&) = delete;
+  FeedNetworkImpl& operator=(FeedNetworkImpl&) = delete;
+
+  // FeedNetwork.
+
+  void SendQueryRequest(
+      const feedwire::Request& request,
+      base::OnceCallback<void(QueryRequestResult)> callback) override;
+
+  void SendActionRequest(
+      const feedwire::ActionRequest& request,
+      base::OnceCallback<void(ActionRequestResult)> callback) override;
+
+  // Cancels all pending requests immediately. This could be used, for example,
+  // if there are pending requests for a user who just signed out.
+  void CancelRequests() override;
+
+ private:
+  // Start a request to |url| of type |request_type| with body |request_body|.
+  // |callback| will be called when the response is received or if there is
+  // an error, including non-protocol errors. The contents of |request_body|
+  // will be gzipped.
+  void Send(const GURL& url,
+            const std::string& request_type,
+            std::string request_body,
+            base::OnceCallback<void(FeedNetworkImpl::RawResponse)> callback);
+
+  void SendComplete(NetworkFetch* fetch,
+                    base::OnceCallback<void(RawResponse)> callback,
+                    RawResponse raw_response);
+
+  Delegate* delegate_;
+  signin::IdentityManager* identity_manager_;
+  const std::string api_key_;
+  scoped_refptr<network::SharedURLLoaderFactory> loader_factory_;
+  const base::TickClock* tick_clock_;
+  PrefService* pref_service_;
+  base::flat_set<std::unique_ptr<NetworkFetch>, base::UniquePtrComparator>
+      pending_requests_;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_FEED_NETWORK_IMPL_H_
diff --git a/chromium/components/feed/core/v2/feed_network_impl_unittest.cc b/chromium/components/feed/core/v2/feed_network_impl_unittest.cc
new file mode 100644
index 00000000000..7170cd5b8f1
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_network_impl_unittest.cc
@@ -0,0 +1,413 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_network_impl.h"
+
+#include <memory>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/test/bind_test_util.h"
+#include "base/test/metrics/histogram_tester.h"
+#include "base/test/simple_test_tick_clock.h"
+#include "base/test/task_environment.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/proto/v2/wire/action_request.pb.h"
+#include "components/feed/core/proto/v2/wire/feed_action_response.pb.h"
+#include "components/feed/core/proto/v2/wire/request.pb.h"
+#include "components/feed/core/proto/v2/wire/response.pb.h"
+#include "components/feed/core/v2/test/callback_receiver.h"
+#include "components/prefs/testing_pref_service.h"
+#include "components/signin/public/identity_manager/identity_test_environment.h"
+#include "net/http/http_response_headers.h"
+#include "net/http/http_status_code.h"
+#include "net/http/http_util.h"
+#include "net/traffic_annotation/network_traffic_annotation_test_helper.h"
+#include "services/network/public/cpp/url_loader_completion_status.h"
+#include "services/network/public/cpp/weak_wrapper_shared_url_loader_factory.h"
+#include "services/network/test/test_url_loader_factory.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/zlib/google/compression_utils.h"
+#include "url/gurl.h"
+
+namespace feed {
+namespace {
+
+using base::TimeDelta;
+using testing::ElementsAre;
+using ActionRequestResult = FeedNetwork::ActionRequestResult;
+using QueryRequestResult = FeedNetwork::QueryRequestResult;
+
+feedwire::Request GetTestFeedRequest(feedwire::FeedQuery::RequestReason reason =
+                                         feedwire::FeedQuery::MANUAL_REFRESH) {
+  feedwire::Request request;
+  request.set_request_version(feedwire::Request::FEED_QUERY);
+  request.mutable_feed_request()->mutable_feed_query()->set_reason(reason);
+  return request;
+}
+
+feedwire::Response GetTestFeedResponse() {
+  feedwire::Response response;
+  response.set_response_version(feedwire::Response::FEED_RESPONSE);
+  return response;
+}
+
+feedwire::ActionRequest GetTestActionRequest() {
+  feedwire::ActionRequest request;
+  request.set_request_version(feedwire::ActionRequest::FEED_UPLOAD_ACTION);
+  return request;
+}
+
+feedwire::FeedActionResponse GetTestActionResponse() {
+  feedwire::FeedActionResponse response;
+  response.mutable_consistency_token()->set_token("tok");
+  return response;
+}
+
+class TestDelegate : public FeedNetworkImpl::Delegate {
+ public:
+  std::string GetLanguageTag() override { return "en"; }
+};
+
+class FeedNetworkTest : public testing::Test {
+ public:
+  FeedNetworkTest() {
+    identity_test_env_.MakePrimaryAccountAvailable("example@gmail.com");
+    identity_test_env_.SetAutomaticIssueOfAccessTokens(true);
+  }
+  FeedNetworkTest(FeedNetworkTest&) = delete;
+  FeedNetworkTest& operator=(const FeedNetworkTest&) = delete;
+  ~FeedNetworkTest() override = default;
+
+  void SetUp() override {
+    feed::RegisterProfilePrefs(profile_prefs_.registry());
+
+    shared_url_loader_factory_ =
+        base::MakeRefCounted<network::WeakWrapperSharedURLLoaderFactory>(
+            &test_factory_);
+    feed_network_ = std::make_unique<FeedNetworkImpl>(
+        &delegate_, identity_test_env_.identity_manager(), "dummy_api_key",
+        shared_url_loader_factory_, task_environment_.GetMockTickClock(),
+        &profile_prefs_);
+  }
+
+  FeedNetwork* feed_network() { return feed_network_.get(); }
+
+  signin::IdentityTestEnvironment* identity_env() {
+    return &identity_test_env_;
+  }
+
+  network::TestURLLoaderFactory* test_factory() { return &test_factory_; }
+
+  base::test::TaskEnvironment task_environment_{
+      base::test::TaskEnvironment::TimeSource::MOCK_TIME};
+
+  TestingPrefServiceSimple& profile_prefs() { return profile_prefs_; }
+
+  void Respond(const GURL& url,
+               const std::string& response_string,
+               net::HttpStatusCode code = net::HTTP_OK,
+               network::URLLoaderCompletionStatus status =
+                   network::URLLoaderCompletionStatus()) {
+    auto head = network::mojom::URLResponseHead::New();
+    if (code >= 0) {
+      if (response_headers_) {
+        head->headers = response_headers_;
+      } else {
+        head->headers = base::MakeRefCounted<net::HttpResponseHeaders>(
+            "HTTP/1.1 " + base::NumberToString(code));
+      }
+      status.decoded_body_length = response_string.length();
+    }
+
+    test_factory_.AddResponse(url, std::move(head), response_string, status);
+  }
+
+  network::ResourceRequest RespondToQueryRequest(
+      const std::string& response_string,
+      net::HttpStatusCode code) {
+    task_environment_.RunUntilIdle();
+    network::TestURLLoaderFactory::PendingRequest* pending_request =
+        test_factory()->GetPendingRequest(0);
+    CHECK(pending_request);
+    network::ResourceRequest resource_request = pending_request->request;
+    Respond(pending_request->request.url, response_string, code);
+    task_environment_.FastForwardUntilNoTasksRemain();
+    return resource_request;
+  }
+
+  network::ResourceRequest RespondToQueryRequest(
+      feedwire::Response response_message,
+      net::HttpStatusCode code) {
+    std::string binary_proto;
+    response_message.SerializeToString(&binary_proto);
+    return RespondToQueryRequest(binary_proto, code);
+  }
+
+  network::ResourceRequest RespondToActionRequest(
+      feedwire::FeedActionResponse response_message,
+      net::HttpStatusCode code) {
+    std::string binary_proto;
+    response_message.SerializeToString(&binary_proto);
+    return RespondToQueryRequest(binary_proto, code);
+  }
+
+ protected:
+  scoped_refptr<net::HttpResponseHeaders> response_headers_;
+
+ private:
+  TestDelegate delegate_;
+  signin::IdentityTestEnvironment identity_test_env_;
+  std::unique_ptr<FeedNetwork> feed_network_;
+  network::TestURLLoaderFactory test_factory_;
+  scoped_refptr<network::SharedURLLoaderFactory> shared_url_loader_factory_;
+  base::SimpleTestTickClock test_tick_clock_;
+  TestingPrefServiceSimple profile_prefs_;
+};
+
+TEST_F(FeedNetworkTest, SendQueryRequestEmpty) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(feedwire::Request(), receiver.Bind());
+
+  ASSERT_TRUE(receiver.GetResult());
+  const QueryRequestResult& result = *receiver.GetResult();
+  EXPECT_EQ(0, result.status_code);
+  EXPECT_FALSE(result.response_body);
+}
+
+TEST_F(FeedNetworkTest, SendQueryRequestSendsValidRequest) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  network::ResourceRequest resource_request =
+      RespondToQueryRequest("", net::HTTP_OK);
+
+  EXPECT_EQ(
+      "https://www.google.com/httpservice/retry/InteractiveDiscoverAgaService/"
+      "FeedQuery?reqpld=%08%01%C2%3E%04%12%02%08%01&fmt=bin&hl=en",
+      resource_request.url);
+  EXPECT_EQ("GET", resource_request.method);
+  EXPECT_FALSE(resource_request.headers.HasHeader("content-encoding"));
+  std::string authorization;
+  EXPECT_TRUE(
+      resource_request.headers.GetHeader("Authorization", &authorization));
+  EXPECT_EQ(authorization, "Bearer access_token");
+}
+
+TEST_F(FeedNetworkTest, SendQueryRequestInvalidResponse) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  RespondToQueryRequest("invalid", net::HTTP_OK);
+
+  ASSERT_TRUE(receiver.GetResult());
+  const QueryRequestResult& result = *receiver.GetResult();
+  EXPECT_EQ(net::HTTP_OK, result.status_code);
+  EXPECT_FALSE(result.response_body);
+}
+
+TEST_F(FeedNetworkTest, SendQueryRequestReceivesResponse) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_OK);
+
+  ASSERT_TRUE(receiver.GetResult());
+  const QueryRequestResult& result = *receiver.GetResult();
+  EXPECT_EQ(net::HTTP_OK, result.status_code);
+  EXPECT_EQ(GetTestFeedResponse().response_version(),
+            result.response_body->response_version());
+}
+
+TEST_F(FeedNetworkTest, SendQueryRequestIgnoresBodyForNon200Response) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_FORBIDDEN);
+
+  ASSERT_TRUE(receiver.GetResult());
+  const QueryRequestResult& result = *receiver.GetResult();
+  EXPECT_EQ(net::HTTP_FORBIDDEN, result.status_code);
+  EXPECT_FALSE(result.response_body);
+}
+
+TEST_F(FeedNetworkTest, CancelRequest) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  feed_network()->CancelRequests();
+  task_environment_.FastForwardUntilNoTasksRemain();
+
+  EXPECT_FALSE(receiver.GetResult());
+}
+
+TEST_F(FeedNetworkTest, RequestTimeout) {
+  base::HistogramTester histogram_tester;
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  task_environment_.FastForwardBy(TimeDelta::FromSeconds(30));
+
+  ASSERT_TRUE(receiver.GetResult());
+  const QueryRequestResult& result = *receiver.GetResult();
+  EXPECT_EQ(net::ERR_TIMED_OUT, result.status_code);
+  histogram_tester.ExpectTimeBucketCount(
+      "ContentSuggestions.Feed.Network.Duration", TimeDelta::FromSeconds(30),
+      1);
+}
+
+TEST_F(FeedNetworkTest, ParallelRequests) {
+  CallbackReceiver<QueryRequestResult> receiver1, receiver2;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver1.Bind());
+  // Make another request with a different URL so Respond() won't affect both
+  // requests.
+  feed_network()->SendQueryRequest(
+      GetTestFeedRequest(feedwire::FeedQuery::NEXT_PAGE_SCROLL),
+      receiver2.Bind());
+
+  // Respond to both requests, avoiding FastForwardUntilNoTasksRemain until
+  // a response is added for both requests.
+  ASSERT_EQ(2, test_factory()->NumPending());
+  for (int i = 0; i < 2; ++i) {
+    network::TestURLLoaderFactory::PendingRequest* pending_request =
+        test_factory()->GetPendingRequest(0);
+    ASSERT_TRUE(pending_request) << "for request #" << i;
+    std::string binary_proto;
+    GetTestFeedResponse().SerializeToString(&binary_proto);
+    Respond(pending_request->request.url, binary_proto, net::HTTP_OK);
+  }
+  task_environment_.FastForwardUntilNoTasksRemain();
+
+  EXPECT_TRUE(receiver1.GetResult());
+  EXPECT_TRUE(receiver2.GetResult());
+}
+
+TEST_F(FeedNetworkTest, ShouldReportRequestStatusCode) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  base::HistogramTester histogram_tester;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_FORBIDDEN);
+  EXPECT_THAT(
+      histogram_tester.GetAllSamples(
+          "ContentSuggestions.Feed.Network.RequestStatusCode"),
+      ElementsAre(base::Bucket(/*min=*/net::HTTP_FORBIDDEN, /*count=*/1)));
+}
+
+TEST_F(FeedNetworkTest, ShouldIncludeAPIKeyForAuthError) {
+  identity_env()->SetAutomaticIssueOfAccessTokens(false);
+  CallbackReceiver<QueryRequestResult> receiver;
+  base::HistogramTester histogram_tester;
+
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  identity_env()->WaitForAccessTokenRequestIfNecessaryAndRespondWithError(
+      GoogleServiceAuthError(
+          GoogleServiceAuthError::State::INVALID_GAIA_CREDENTIALS));
+
+  network::ResourceRequest resource_request =
+      RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_OK);
+
+  EXPECT_THAT(resource_request.url.spec(),
+              testing::HasSubstr("key=dummy_api_key"));
+
+  EXPECT_THAT(
+      histogram_tester.GetAllSamples(
+          "ContentSuggestions.Feed.Network.TokenFetchStatus"),
+      testing::ElementsAre(base::Bucket(
+          /*min=*/GoogleServiceAuthError::State::INVALID_GAIA_CREDENTIALS,
+          /*count=*/1)));
+}
+
+// Disabled for chromeos, which doesn't allow for there not to be a signed in
+// user.
+#if !defined(OS_CHROMEOS)
+TEST_F(FeedNetworkTest, ShouldIncludeAPIKeyForNoSignedInUser) {
+  identity_env()->ClearPrimaryAccount();
+  CallbackReceiver<QueryRequestResult> receiver;
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+
+  network::ResourceRequest resource_request =
+      RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_OK);
+
+  EXPECT_THAT(resource_request.url.spec(),
+              testing::HasSubstr("key=dummy_api_key"));
+}
+#endif
+
+TEST_F(FeedNetworkTest, TestDurationHistogram) {
+  base::HistogramTester histogram_tester;
+  CallbackReceiver<QueryRequestResult> receiver;
+  const TimeDelta kDuration = TimeDelta::FromMilliseconds(12345);
+
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+  task_environment_.FastForwardBy(kDuration);
+  RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_OK);
+
+  EXPECT_TRUE(receiver.GetResult());
+  histogram_tester.ExpectTimeBucketCount(
+      "ContentSuggestions.Feed.Network.Duration", kDuration, 1);
+}
+
+// Verify that the kHostOverrideHost pref overrides the feed host
+// and updates the Bless nonce if one sent in the response.
+TEST_F(FeedNetworkTest, TestHostOverrideWithAuthHeader) {
+  CallbackReceiver<QueryRequestResult> receiver;
+  profile_prefs().SetString(feed::prefs::kHostOverrideHost,
+                            "http://www.newhost.com/");
+  feed_network()->SendQueryRequest(GetTestFeedRequest(), receiver.Bind());
+
+  response_headers_ = base::MakeRefCounted<net::HttpResponseHeaders>(
+      net::HttpUtil::AssembleRawHeaders(
+          "HTTP/1.1 401 Unauthorized\nwww-authenticate: Foo "
+          "nonce=\"1234123412341234\"\n\n"));
+  RespondToQueryRequest(GetTestFeedResponse(), net::HTTP_FORBIDDEN);
+
+  EXPECT_TRUE(receiver.GetResult());
+  EXPECT_EQ("1234123412341234",
+            profile_prefs().GetString(feed::prefs::kHostOverrideBlessNonce));
+}
+
+TEST_F(FeedNetworkTest, SendActionRequest) {
+  CallbackReceiver<ActionRequestResult> receiver;
+  feed_network()->SendActionRequest(GetTestActionRequest(), receiver.Bind());
+  RespondToActionRequest(GetTestActionResponse(), net::HTTP_OK);
+
+  ASSERT_TRUE(receiver.GetResult());
+  const ActionRequestResult& result = *receiver.GetResult();
+  EXPECT_EQ(net::HTTP_OK, result.status_code);
+  EXPECT_TRUE(result.response_body);
+}
+
+TEST_F(FeedNetworkTest, SendActionRequestSendsValidRequest) {
+  CallbackReceiver<ActionRequestResult> receiver;
+  feed_network()->SendActionRequest(GetTestActionRequest(), receiver.Bind());
+  network::ResourceRequest resource_request =
+      RespondToActionRequest(GetTestActionResponse(), net::HTTP_OK);
+
+  EXPECT_EQ(
+      GURL("https://www.google.com/httpservice/retry/ClankActionUploadService/"
+           "ClankActionUpload?fmt=bin&hl=en"),
+      resource_request.url);
+
+  EXPECT_EQ("POST", resource_request.method);
+  std::string content_encoding;
+  EXPECT_TRUE(resource_request.headers.GetHeader("content-encoding",
+                                                 &content_encoding));
+  EXPECT_EQ("gzip", content_encoding);
+  std::string authorization;
+  EXPECT_TRUE(
+      resource_request.headers.GetHeader("Authorization", &authorization));
+  EXPECT_EQ(authorization, "Bearer access_token");
+
+  // Check that the body content is correct. This requires some work to extract
+  // the bytes and unzip them.
+  auto* elements = resource_request.request_body->elements();
+  ASSERT_TRUE(elements);
+  ASSERT_EQ(1UL, elements->size());
+  std::string sent_body((*elements)[0].bytes(), (*elements)[0].length());
+  std::string sent_body_uncompressed;
+  ASSERT_TRUE(compression::GzipUncompress(sent_body, &sent_body_uncompressed));
+  std::string expected_body;
+  ASSERT_TRUE(GetTestActionRequest().SerializeToString(&expected_body));
+  EXPECT_EQ(expected_body, sent_body_uncompressed);
+}
+
+}  // namespace
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/feed_store.cc b/chromium/components/feed/core/v2/feed_store.cc
new file mode 100644
index 00000000000..7321e84fa8f
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_store.cc
@@ -0,0 +1,388 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_store.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/containers/flat_set.h"
+#include "base/files/file_path.h"
+#include "base/logging.h"
+#include "base/strings/strcat.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/task/post_task.h"
+#include "base/task/thread_pool.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+#include "components/leveldb_proto/public/proto_database_provider.h"
+
+namespace feed {
+namespace {
+
+// Keys are defined as:
+// 'S/<stream-id>' -> stream_data
+// 'T/<stream-id>/<sequence-number>' -> stream_structures
+// 'c/<content-id>' -> content
+// 'a/<id>' -> action
+// 's/<content-id>' -> shared_state
+// 'N' -> next_stream_state
+constexpr char kMainStreamId[] = "0";
+const char kStreamDataKey[] = "S/0";
+const char kLocalActionPrefix[] = "a/";
+const char kNextStreamStateKey[] = "N";
+
+leveldb::ReadOptions CreateReadOptions() {
+  leveldb::ReadOptions opts;
+  opts.fill_cache = false;
+  return opts;
+}
+
+std::string KeyForContentId(base::StringPiece prefix,
+                            const feedwire::ContentId& content_id) {
+  return base::StrCat({prefix, content_id.content_domain(), ",",
+                       base::NumberToString(content_id.type()), ",",
+                       base::NumberToString(content_id.id())});
+}
+
+std::string ContentKey(const feedwire::ContentId& content_id) {
+  return KeyForContentId("c/", content_id);
+}
+
+std::string SharedStateKey(const feedwire::ContentId& content_id) {
+  return KeyForContentId("s/", content_id);
+}
+
+std::string KeyForRecord(const feedstore::Record& record) {
+  switch (record.data_case()) {
+    case feedstore::Record::kStreamData:
+      return kStreamDataKey;
+    case feedstore::Record::kStreamStructures:
+      return base::StrCat(
+          {"T/", record.stream_structures().stream_id(), "/",
+           base::NumberToString(record.stream_structures().sequence_number())});
+    case feedstore::Record::kContent:
+      return ContentKey(record.content().content_id());
+    case feedstore::Record::kLocalAction:
+      return kLocalActionPrefix +
+             base::NumberToString(record.local_action().id());
+    case feedstore::Record::kSharedState:
+      return SharedStateKey(record.shared_state().content_id());
+    case feedstore::Record::kNextStreamState:
+      return kNextStreamStateKey;
+    case feedstore::Record::DATA_NOT_SET:  // fall through
+      NOTREACHED() << "Invalid record case " << record.data_case();
+      return "";
+  }
+}
+
+bool FilterByKey(const base::flat_set<std::string>& key_set,
+                 const std::string& key) {
+  return key_set.contains(key);
+}
+
+feedstore::Record MakeRecord(feedstore::Content content) {
+  feedstore::Record record;
+  *record.mutable_content() = std::move(content);
+  return record;
+}
+
+feedstore::Record MakeRecord(
+    feedstore::StreamStructureSet stream_structure_set) {
+  feedstore::Record record;
+  *record.mutable_stream_structures() = std::move(stream_structure_set);
+  return record;
+}
+
+feedstore::Record MakeRecord(feedstore::StreamSharedState shared_state) {
+  feedstore::Record record;
+  *record.mutable_shared_state() = std::move(shared_state);
+  return record;
+}
+
+feedstore::Record MakeRecord(feedstore::StreamData stream_data) {
+  feedstore::Record record;
+  *record.mutable_stream_data() = std::move(stream_data);
+  return record;
+}
+
+template <typename T>
+std::pair<std::string, feedstore::Record> MakeKeyAndRecord(T record_data) {
+  std::pair<std::string, feedstore::Record> result;
+  result.second = MakeRecord(std::move(record_data));
+  result.first = KeyForRecord(result.second);
+  return result;
+}
+
+}  // namespace
+
+FeedStore::LoadStreamResult::LoadStreamResult() = default;
+FeedStore::LoadStreamResult::~LoadStreamResult() = default;
+FeedStore::LoadStreamResult::LoadStreamResult(LoadStreamResult&&) = default;
+FeedStore::LoadStreamResult& FeedStore::LoadStreamResult::operator=(
+    LoadStreamResult&&) = default;
+
+FeedStore::FeedStore(
+    std::unique_ptr<leveldb_proto::ProtoDatabase<feedstore::Record>> database)
+    : database_status_(leveldb_proto::Enums::InitStatus::kNotInitialized),
+      database_(std::move(database)) {
+}
+
+FeedStore::~FeedStore() = default;
+
+void FeedStore::Initialize(base::OnceClosure initialize_complete) {
+  if (IsInitialized()) {
+    std::move(initialize_complete).Run();
+  } else {
+    initialize_callback_ = std::move(initialize_complete);
+    database_->Init(base::BindOnce(&FeedStore::OnDatabaseInitialized,
+                                   weak_ptr_factory_.GetWeakPtr()));
+  }
+}
+
+void FeedStore::OnDatabaseInitialized(leveldb_proto::Enums::InitStatus status) {
+  database_status_ = status;
+  if (initialize_callback_)
+    std::move(initialize_callback_).Run();
+}
+
+bool FeedStore::IsInitialized() const {
+  return database_status_ == leveldb_proto::Enums::InitStatus::kOK;
+}
+
+bool FeedStore::IsInitializedForTesting() const {
+  return IsInitialized();
+}
+
+void FeedStore::ReadSingle(
+    const std::string& key,
+    base::OnceCallback<void(bool, std::unique_ptr<feedstore::Record>)>
+        callback) {
+  if (!IsInitialized()) {
+    std::move(callback).Run(false, nullptr);
+    return;
+  }
+
+  database_->GetEntry(key, std::move(callback));
+}
+
+void FeedStore::ReadMany(
+    const base::flat_set<std::string>& key_set,
+    base::OnceCallback<
+        void(bool, std::unique_ptr<std::vector<feedstore::Record>>)> callback) {
+  if (!IsInitialized()) {
+    std::move(callback).Run(false, nullptr);
+    return;
+  }
+
+  database_->LoadEntriesWithFilter(
+      base::BindRepeating(&FilterByKey, std::move(key_set)),
+      CreateReadOptions(),
+      /*target_prefix=*/"", std::move(callback));
+}
+
+void FeedStore::LoadStream(
+    base::OnceCallback<void(LoadStreamResult)> callback) {
+  if (!IsInitialized()) {
+    LoadStreamResult result;
+    result.read_error = true;
+    std::move(callback).Run(std::move(result));
+    return;
+  }
+  auto filter = [](const std::string& key) {
+    return key == "S/0" || (key.size() > 3 && key[0] == 'T' && key[1] == '/' &&
+                            key[2] == '0' && key[3] == '/');
+  };
+  database_->LoadEntriesWithFilter(
+      base::BindRepeating(filter), CreateReadOptions(),
+      /*target_prefix=*/"",
+      base::BindOnce(&FeedStore::OnLoadStreamFinished, base::Unretained(this),
+                     std::move(callback)));
+}
+
+void FeedStore::OnLoadStreamFinished(
+    base::OnceCallback<void(LoadStreamResult)> callback,
+    bool success,
+    std::unique_ptr<std::vector<feedstore::Record>> records) {
+  LoadStreamResult result;
+  if (!records || !success) {
+    result.read_error = true;
+  } else {
+    for (feedstore::Record& record : *records) {
+      if (record.has_stream_structures()) {
+        result.stream_structures.push_back(
+            std::move(*record.mutable_stream_structures()));
+      } else if (record.has_stream_data()) {
+        result.stream_data = std::move(*record.mutable_stream_data());
+      }
+    }
+  }
+  std::move(callback).Run(std::move(result));
+}
+
+void FeedStore::SaveFullStream(
+    std::unique_ptr<StreamModelUpdateRequest> update_request,
+    base::OnceCallback<void(bool)> callback) {
+  auto updates = std::make_unique<
+      std::vector<std::pair<std::string, feedstore::Record>>>();
+  updates->push_back(MakeKeyAndRecord(std::move(update_request->stream_data)));
+  for (feedstore::Content& content : update_request->content) {
+    updates->push_back(MakeKeyAndRecord(std::move(content)));
+  }
+  for (feedstore::StreamSharedState& shared_state :
+       update_request->shared_states) {
+    updates->push_back(MakeKeyAndRecord(std::move(shared_state)));
+  }
+  feedstore::StreamStructureSet stream_structure_set;
+  stream_structure_set.set_stream_id(kMainStreamId);
+  for (feedstore::StreamStructure& structure :
+       update_request->stream_structures) {
+    *stream_structure_set.add_structures() = std::move(structure);
+  }
+  updates->push_back(MakeKeyAndRecord(std::move(stream_structure_set)));
+
+  // Set up a filter to delete all stream-related data.
+  // But we need to exclude keys being written right now.
+  std::vector<std::string> key_vector(updates->size());
+  for (size_t i = 0; i < key_vector.size(); ++i) {
+    key_vector[i] = (*updates)[i].first;
+  }
+  base::flat_set<std::string> updated_keys(std::move(key_vector));
+
+  auto filter = [](const base::flat_set<std::string>& updated_keys,
+                   const std::string& key) {
+    if (key.empty() || updated_keys.contains(key))
+      return false;
+    return key[0] == 'S' || key[0] == 'T' || key[0] == 'c' || key[0] == 's' ||
+           key[0] == 'N';
+  };
+
+  database_->UpdateEntriesWithRemoveFilter(
+      std::move(updates), base::BindRepeating(filter, std::move(updated_keys)),
+      base::BindOnce(&FeedStore::OnSaveStreamEntriesUpdated,
+                     base::Unretained(this), std::move(callback)));
+}
+
+void FeedStore::OnSaveStreamEntriesUpdated(
+    base::OnceCallback<void(bool)> complete_callback,
+    bool ok) {
+  std::move(complete_callback).Run(ok);
+}
+
+void FeedStore::WriteOperations(
+    int32_t sequence_number,
+    std::vector<feedstore::DataOperation> operations) {
+  std::vector<feedstore::Record> records;
+  feedstore::Record structures_record;
+  feedstore::StreamStructureSet& structure_set =
+      *structures_record.mutable_stream_structures();
+  for (feedstore::DataOperation& operation : operations) {
+    *structure_set.add_structures() = std::move(*operation.mutable_structure());
+    if (operation.has_content()) {
+      feedstore::Record record;
+      record.set_allocated_content(operation.release_content());
+      records.push_back(std::move(record));
+    }
+  }
+  structure_set.set_stream_id(kMainStreamId);
+  structure_set.set_sequence_number(sequence_number);
+
+  records.push_back(std::move(structures_record));
+  Write(std::move(records), base::DoNothing());
+}
+
+void FeedStore::ReadContent(
+    std::vector<feedwire::ContentId> content_ids,
+    std::vector<feedwire::ContentId> shared_state_ids,
+    base::OnceCallback<void(std::vector<feedstore::Content>,
+                            std::vector<feedstore::StreamSharedState>)>
+        content_callback) {
+  std::vector<std::string> key_vector;
+  key_vector.reserve(content_ids.size() + shared_state_ids.size());
+  for (const auto& content_id : content_ids)
+    key_vector.push_back(ContentKey(content_id));
+  for (const auto& content_id : shared_state_ids)
+    key_vector.push_back(SharedStateKey(content_id));
+
+  for (const auto& shared_state_id : shared_state_ids)
+    key_vector.push_back(SharedStateKey(shared_state_id));
+
+  ReadMany(base::flat_set<std::string>(std::move(key_vector)),
+           base::BindOnce(&FeedStore::OnReadContentFinished,
+                          weak_ptr_factory_.GetWeakPtr(),
+                          std::move(content_callback)));
+}
+
+void FeedStore::OnReadContentFinished(
+    base::OnceCallback<void(std::vector<feedstore::Content>,
+                            std::vector<feedstore::StreamSharedState>)>
+        callback,
+    bool success,
+    std::unique_ptr<std::vector<feedstore::Record>> records) {
+  if (!success || !records) {
+    std::move(callback).Run({}, {});
+    return;
+  }
+
+  std::vector<feedstore::Content> content;
+  // Most of records will be content.
+  content.reserve(records->size());
+  std::vector<feedstore::StreamSharedState> shared_states;
+  for (auto& record : *records) {
+    if (record.data_case() == feedstore::Record::kContent)
+      content.push_back(std::move(record.content()));
+    else if (record.data_case() == feedstore::Record::kSharedState)
+      shared_states.push_back(std::move(record.shared_state()));
+  }
+
+  std::move(callback).Run(std::move(content), std::move(shared_states));
+}
+
+void FeedStore::ReadNextStreamState(
+    base::OnceCallback<void(std::unique_ptr<feedstore::StreamAndContentState>)>
+        callback) {
+  ReadSingle(
+      kNextStreamStateKey,
+      base::BindOnce(&FeedStore::OnReadNextStreamStateFinished,
+                     weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
+}
+
+void FeedStore::OnReadNextStreamStateFinished(
+    base::OnceCallback<void(std::unique_ptr<feedstore::StreamAndContentState>)>
+        callback,
+    bool success,
+    std::unique_ptr<feedstore::Record> record) {
+  if (!success || !record) {
+    std::move(callback).Run(nullptr);
+    return;
+  }
+
+  std::move(callback).Run(
+      base::WrapUnique(record->release_next_stream_state()));
+}
+
+void FeedStore::Write(std::vector<feedstore::Record> records,
+                      base::OnceCallback<void(bool)> callback) {
+  auto entries_to_save = std::make_unique<
+      leveldb_proto::ProtoDatabase<feedstore::Record>::KeyEntryVector>();
+  for (auto& record : records) {
+    std::string key = KeyForRecord(record);
+    if (!key.empty())
+      entries_to_save->push_back({std::move(key), std::move(record)});
+  }
+
+  database_->UpdateEntries(
+      std::move(entries_to_save),
+      /*keys_to_remove=*/std::make_unique<leveldb_proto::KeyVector>(),
+      base::BindOnce(&FeedStore::OnWriteFinished,
+                     weak_ptr_factory_.GetWeakPtr(), std::move(callback)));
+}
+
+void FeedStore::OnWriteFinished(base::OnceCallback<void(bool)> callback,
+                                bool success) {
+  std::move(callback).Run(success);
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/feed_store.h b/chromium/components/feed/core/v2/feed_store.h
new file mode 100644
index 00000000000..3ae93ead5b6
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_store.h
@@ -0,0 +1,129 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_FEED_STORE_H_
+#define COMPONENTS_FEED_CORE_V2_FEED_STORE_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/containers/flat_set.h"
+#include "base/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/leveldb_proto/public/proto_database.h"
+#include "components/leveldb_proto/public/proto_database_provider.h"
+
+namespace feed {
+struct StreamModelUpdateRequest;
+
+class FeedStore {
+ public:
+  struct LoadStreamResult {
+    LoadStreamResult();
+    ~LoadStreamResult();
+    LoadStreamResult(LoadStreamResult&&);
+    LoadStreamResult& operator=(LoadStreamResult&&);
+    LoadStreamResult(const LoadStreamResult&) = delete;
+    LoadStreamResult& operator=(const LoadStreamResult&) = delete;
+
+    bool read_error = false;
+    feedstore::StreamData stream_data;
+    std::vector<feedstore::StreamStructureSet> stream_structures;
+  };
+
+  explicit FeedStore(
+      std::unique_ptr<leveldb_proto::ProtoDatabase<feedstore::Record>>
+          database);
+  ~FeedStore();
+  FeedStore(const FeedStore&) = delete;
+  FeedStore& operator=(const FeedStore&) = delete;
+
+  void Initialize(base::OnceClosure initialize_complete);
+
+  void LoadStream(base::OnceCallback<void(LoadStreamResult)> callback);
+
+  void SaveFullStream(std::unique_ptr<StreamModelUpdateRequest> update_request,
+                      base::OnceCallback<void(bool)> callback);
+
+  void WriteOperations(int32_t sequence_number,
+                       std::vector<feedstore::DataOperation> operations);
+
+  // Read StreamData and pass it to stream_data_callback, or nullptr on failure.
+  void ReadStreamData(
+      base::OnceCallback<void(std::unique_ptr<feedstore::StreamData>)>
+          stream_data_callback);
+
+  // Read Content and StreamSharedStates and pass them to content_callback, or
+  // nullptrs on failure.
+  void ReadContent(
+      std::vector<feedwire::ContentId> content_ids,
+      std::vector<feedwire::ContentId> shared_state_ids,
+      base::OnceCallback<void(std::vector<feedstore::Content>,
+                              std::vector<feedstore::StreamSharedState>)>
+          content_callback);
+
+  void ReadNextStreamState(
+      base::OnceCallback<
+          void(std::unique_ptr<feedstore::StreamAndContentState>)> callback);
+
+  // TODO(iwells): implement reading stored actions
+
+  // TODO(iwells): implement this
+  // Deletes old records that are no longer needed
+  // void RemoveOldData(base::OnceCallback<void(bool)> callback);
+
+  bool IsInitializedForTesting() const;
+
+ private:
+  void OnDatabaseInitialized(leveldb_proto::Enums::InitStatus status);
+  bool IsInitialized() const;
+
+  void Write(std::vector<feedstore::Record> records,
+             base::OnceCallback<void(bool)> callback);
+
+  void ReadSingle(
+      const std::string& key,
+      base::OnceCallback<void(bool, std::unique_ptr<feedstore::Record>)>
+          callback);
+  void ReadMany(const base::flat_set<std::string>& key_set,
+                base::OnceCallback<
+                    void(bool, std::unique_ptr<std::vector<feedstore::Record>>)>
+                    callback);
+  void OnSaveStreamEntriesUpdated(
+      base::OnceCallback<void(bool)> complete_callback,
+      bool ok);
+  void OnLoadStreamFinished(
+      base::OnceCallback<void(LoadStreamResult)> callback,
+      bool success,
+      std::unique_ptr<std::vector<feedstore::Record>> records);
+  void OnReadContentFinished(
+      base::OnceCallback<void(std::vector<feedstore::Content>,
+                              std::vector<feedstore::StreamSharedState>)>
+          callback,
+      bool success,
+      std::unique_ptr<std::vector<feedstore::Record>> records);
+  void OnReadNextStreamStateFinished(
+      base::OnceCallback<
+          void(std::unique_ptr<feedstore::StreamAndContentState>)> callback,
+      bool success,
+      std::unique_ptr<feedstore::Record> record);
+
+  void OnWriteFinished(base::OnceCallback<void(bool)> callback, bool success);
+
+  // TODO(iwells): implement
+  // bool OldRecordFilter(const std::string& key);
+  // void OnRemoveOldDataFinished(base::OnceCallback<void(bool)> callback,
+  //                             bool success);
+
+  base::OnceClosure initialize_callback_;
+  leveldb_proto::Enums::InitStatus database_status_;
+  std::unique_ptr<leveldb_proto::ProtoDatabase<feedstore::Record>> database_;
+  base::WeakPtrFactory<FeedStore> weak_ptr_factory_{this};
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_FEED_STORE_H_
diff --git a/chromium/components/feed/core/v2/feed_store_unittest.cc b/chromium/components/feed/core/v2/feed_store_unittest.cc
new file mode 100644
index 00000000000..28e2043fc12
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_store_unittest.cc
@@ -0,0 +1,454 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_store.h"
+
+#include <map>
+#include <set>
+#include <utility>
+
+#include "base/strings/strcat.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/test/bind_test_util.h"
+#include "base/test/task_environment.h"
+#include "components/feed/core/proto/v2/wire/content_id.pb.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+#include "components/feed/core/v2/test/callback_receiver.h"
+#include "components/feed/core/v2/test/proto_printer.h"
+#include "components/feed/core/v2/test/stream_builder.h"
+#include "components/leveldb_proto/testing/fake_db.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace feed {
+namespace {
+
+const char kNextPageToken[] = "next page token";
+const char kConsistencyToken[] = "consistency token";
+const int64_t kLastAddedTimeMs = 100;
+
+using LoadStreamResult = FeedStore::LoadStreamResult;
+
+feedstore::StreamData MakeStreamData() {
+  feedstore::StreamData stream_data;
+  *stream_data.mutable_content_id() = MakeRootId();
+  stream_data.set_next_page_token(kNextPageToken);
+  stream_data.set_consistency_token(kConsistencyToken);
+  stream_data.set_last_added_time_millis(kLastAddedTimeMs);
+
+  return stream_data;
+}
+
+std::string KeyForContentId(base::StringPiece prefix,
+                            const feedwire::ContentId& content_id) {
+  return base::StrCat({prefix, content_id.content_domain(), ",",
+                       base::NumberToString(content_id.type()), ",",
+                       base::NumberToString(content_id.id())});
+}
+
+feedstore::Record RecordForContent(feedstore::Content content) {
+  feedstore::Record record;
+  *record.mutable_content() = std::move(content);
+  return record;
+}
+
+feedstore::Record RecordForSharedState(feedstore::StreamSharedState shared) {
+  feedstore::Record record;
+  *record.mutable_shared_state() = std::move(shared);
+  return record;
+}
+
+}  // namespace
+
+class FeedStoreTest : public testing::Test {
+ protected:
+  void MakeFeedStore(std::map<std::string, feedstore::Record> entries,
+                     leveldb_proto::Enums::InitStatus init_status =
+                         leveldb_proto::Enums::InitStatus::kOK) {
+    db_entries_ = std::move(entries);
+    auto fake_db =
+        std::make_unique<leveldb_proto::test::FakeDB<feedstore::Record>>(
+            &db_entries_);
+    fake_db_ = fake_db.get();
+    store_ = std::make_unique<FeedStore>(std::move(fake_db));
+    store_->Initialize(base::DoNothing());
+    fake_db_->InitStatusCallback(init_status);
+  }
+
+  std::set<std::string> StoredKeys() {
+    std::set<std::string> result;
+    for (auto& entry : db_entries_) {
+      result.insert(entry.first);
+    }
+    return result;
+  }
+
+  std::string StoreToString() {
+    std::stringstream ss;
+    for (auto& entry : db_entries_) {
+      ss << "[" << entry.first << "] " << entry.second;
+    }
+    return ss.str();
+  }
+
+  base::test::TaskEnvironment task_environment_{
+      base::test::TaskEnvironment::TimeSource::SYSTEM_TIME};
+  std::unique_ptr<FeedStore> store_;
+  std::map<std::string, feedstore::Record> db_entries_;
+  leveldb_proto::test::FakeDB<feedstore::Record>* fake_db_;
+};
+
+TEST_F(FeedStoreTest, InitSuccess) {
+  MakeFeedStore({});
+  EXPECT_TRUE(store_->IsInitializedForTesting());
+}
+
+TEST_F(FeedStoreTest, InitFailure) {
+  std::map<std::string, feedstore::Record> entries;
+  auto fake_db =
+      std::make_unique<leveldb_proto::test::FakeDB<feedstore::Record>>(
+          &entries);
+  leveldb_proto::test::FakeDB<feedstore::Record>* fake_db_raw = fake_db.get();
+  auto store = std::make_unique<FeedStore>(std::move(fake_db));
+
+  store->Initialize(base::DoNothing());
+  EXPECT_FALSE(store->IsInitializedForTesting());
+
+  fake_db_raw->InitStatusCallback(leveldb_proto::Enums::InitStatus::kError);
+  EXPECT_FALSE(store->IsInitializedForTesting());
+}
+
+TEST_F(FeedStoreTest, SaveFullStream) {
+  MakeFeedStore({});
+  CallbackReceiver<bool> receiver;
+  store_->SaveFullStream(MakeTypicalInitialModelState(), receiver.Bind());
+  fake_db_->UpdateCallback(true);
+
+  ASSERT_TRUE(receiver.GetResult());
+
+  EXPECT_EQ(StoreToString(), R"([S/0] {
+  stream_data {
+    content_id {
+      content_domain: "root"
+    }
+    shared_state_id {
+      content_domain: "render_data"
+    }
+  }
+}
+[T/0/0] {
+  stream_structures {
+    stream_id: "0"
+    structures {
+      operation: 1
+    }
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "root"
+      }
+      type: 1
+    }
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "content"
+        type: 3
+      }
+      parent_id {
+        content_domain: "root"
+      }
+      type: 4
+    }
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "stories"
+        type: 4
+      }
+      parent_id {
+        content_domain: "content"
+        type: 3
+      }
+      type: 3
+    }
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "content"
+        type: 3
+        id: 1
+      }
+      parent_id {
+        content_domain: "root"
+      }
+      type: 4
+    }
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "stories"
+        type: 4
+        id: 1
+      }
+      parent_id {
+        content_domain: "content"
+        type: 3
+        id: 1
+      }
+      type: 3
+    }
+  }
+}
+[c/stories,4,0] {
+  content {
+    content_id {
+      content_domain: "stories"
+      type: 4
+    }
+    frame: "f:0"
+  }
+}
+[c/stories,4,1] {
+  content {
+    content_id {
+      content_domain: "stories"
+      type: 4
+      id: 1
+    }
+    frame: "f:1"
+  }
+}
+[s/render_data,0,0] {
+  shared_state {
+    content_id {
+      content_domain: "render_data"
+    }
+    shared_state_data: "ss:0"
+  }
+}
+)");
+}
+
+TEST_F(FeedStoreTest, SaveFullStreamOverwritesData) {
+  MakeFeedStore({});
+  // Insert some junk that should be removed.
+  db_entries_["S/0"].mutable_local_action()->set_id(6);
+  db_entries_["T/0/0"].mutable_local_action()->set_id(6);
+  db_entries_["T/0/73"].mutable_local_action()->set_id(6);
+  db_entries_["c/stories,4,0"].mutable_local_action()->set_id(6);
+  db_entries_["c/stories,4,1"].mutable_local_action()->set_id(6);
+  db_entries_["c/garbage"].mutable_local_action()->set_id(6);
+  db_entries_["s/render_data,0,0"].mutable_local_action()->set_id(6);
+  db_entries_["s/garbage,0,0"].mutable_local_action()->set_id(6);
+
+  CallbackReceiver<bool> receiver;
+  store_->SaveFullStream(MakeTypicalInitialModelState(), receiver.Bind());
+  fake_db_->UpdateCallback(true);
+
+  ASSERT_TRUE(receiver.GetResult());
+  ASSERT_EQ(std::set<std::string>({
+                "S/0",
+                "T/0/0",
+                "c/stories,4,0",
+                "c/stories,4,1",
+                "s/render_data,0,0",
+            }),
+            StoredKeys());
+
+  for (std::string key : StoredKeys()) {
+    EXPECT_FALSE(db_entries_[key].has_local_action())
+        << "Found local action at key " << key
+        << ", did SaveFullStream erase everything?";
+  }
+}
+
+TEST_F(FeedStoreTest, LoadStreamSuccess) {
+  MakeFeedStore({});
+  store_->SaveFullStream(MakeTypicalInitialModelState(), base::DoNothing());
+  fake_db_->UpdateCallback(true);
+
+  CallbackReceiver<LoadStreamResult> receiver;
+  store_->LoadStream(receiver.Bind());
+  fake_db_->LoadCallback(true);
+
+  ASSERT_TRUE(receiver.GetResult());
+  EXPECT_FALSE(receiver.GetResult()->read_error);
+  EXPECT_EQ(ToTextProto(MakeRootId()),
+            ToTextProto(receiver.GetResult()->stream_data.content_id()));
+}
+
+TEST_F(FeedStoreTest, LoadStreamFail) {
+  MakeFeedStore({});
+  store_->SaveFullStream(MakeTypicalInitialModelState(), base::DoNothing());
+  fake_db_->UpdateCallback(true);
+
+  CallbackReceiver<LoadStreamResult> receiver;
+  store_->LoadStream(receiver.Bind());
+  fake_db_->LoadCallback(false);
+
+  ASSERT_TRUE(receiver.GetResult());
+  EXPECT_TRUE(receiver.GetResult()->read_error);
+}
+
+TEST_F(FeedStoreTest, LoadStreamNoData) {
+  MakeFeedStore({});
+
+  CallbackReceiver<LoadStreamResult> receiver;
+  store_->LoadStream(receiver.Bind());
+  fake_db_->LoadCallback(true);
+
+  ASSERT_TRUE(receiver.GetResult());
+  EXPECT_FALSE(receiver.GetResult()->stream_data.has_content_id());
+}
+
+TEST_F(FeedStoreTest, WriteOperations) {
+  MakeFeedStore({});
+  CallbackReceiver<LoadStreamResult> receiver;
+  store_->WriteOperations(5, {MakeOperation(MakeCluster(2, MakeRootId())),
+                              MakeOperation(MakeCluster(6, MakeRootId()))});
+  fake_db_->UpdateCallback(true);
+
+  EXPECT_EQ(StoreToString(), R"([T/0/5] {
+  stream_structures {
+    stream_id: "0"
+    sequence_number: 5
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "content"
+        type: 3
+        id: 2
+      }
+      parent_id {
+        content_domain: "root"
+      }
+      type: 4
+    }
+    structures {
+      operation: 2
+      content_id {
+        content_domain: "content"
+        type: 3
+        id: 6
+      }
+      parent_id {
+        content_domain: "root"
+      }
+      type: 4
+    }
+  }
+}
+)");
+}
+
+TEST_F(FeedStoreTest, ReadNonexistentContentAndSharedStates) {
+  MakeFeedStore({});
+
+  bool did_read = false;
+  store_->ReadContent(
+      {MakeContentContentId(0)}, {MakeSharedStateContentId(0)},
+      base::BindLambdaForTesting(
+          [&](std::vector<feedstore::Content> content,
+              std::vector<feedstore::StreamSharedState> shared_states) {
+            did_read = true;
+            EXPECT_EQ(content.size(), 0ul);
+            EXPECT_EQ(shared_states.size(), 0ul);
+          }));
+  fake_db_->LoadCallback(true);
+  EXPECT_TRUE(did_read);
+}
+
+TEST_F(FeedStoreTest, ReadContentAndSharedStates) {
+  feedstore::Content content1 = MakeContent(1);
+  feedstore::Content content2 = MakeContent(2);
+  feedstore::StreamSharedState shared1 = MakeSharedState(1);
+  feedstore::StreamSharedState shared2 = MakeSharedState(2);
+
+  MakeFeedStore({{KeyForContentId("c/", content1.content_id()),
+                  RecordForContent(content1)},
+                 {KeyForContentId("c/", content2.content_id()),
+                  RecordForContent(content2)},
+                 {KeyForContentId("s/", shared1.content_id()),
+                  RecordForSharedState(shared1)},
+                 {KeyForContentId("s/", shared2.content_id()),
+                  RecordForSharedState(shared2)}});
+
+  std::vector<feedwire::ContentId> content_ids = {content1.content_id(),
+                                                  content2.content_id()};
+  std::vector<feedwire::ContentId> shared_state_ids = {shared1.content_id(),
+                                                       shared2.content_id()};
+
+  // Successful read
+  bool did_successful_read = false;
+  store_->ReadContent(
+      content_ids, shared_state_ids,
+      base::BindLambdaForTesting(
+          [&](std::vector<feedstore::Content> content,
+              std::vector<feedstore::StreamSharedState> shared_states) {
+            did_successful_read = true;
+            ASSERT_EQ(content.size(), 2ul);
+            EXPECT_EQ(ToTextProto(content[0].content_id()),
+                      ToTextProto(content1.content_id()));
+            EXPECT_EQ(content[0].frame(), content1.frame());
+
+            ASSERT_EQ(shared_states.size(), 2ul);
+            EXPECT_EQ(ToTextProto(shared_states[0].content_id()),
+                      ToTextProto(shared1.content_id()));
+            EXPECT_EQ(shared_states[0].shared_state_data(),
+                      shared1.shared_state_data());
+          }));
+  fake_db_->LoadCallback(true);
+  EXPECT_TRUE(did_successful_read);
+
+  // Failed read
+  bool did_failed_read = false;
+  store_->ReadContent(
+      content_ids, shared_state_ids,
+      base::BindLambdaForTesting(
+          [&](std::vector<feedstore::Content> content,
+              std::vector<feedstore::StreamSharedState> shared_states) {
+            did_failed_read = true;
+            EXPECT_EQ(content.size(), 0ul);
+            EXPECT_EQ(shared_states.size(), 0ul);
+          }));
+  fake_db_->LoadCallback(false);
+  EXPECT_TRUE(did_failed_read);
+}
+
+TEST_F(FeedStoreTest, ReadNextStreamState) {
+  feedstore::Record record;
+  feedstore::StreamAndContentState* next_stream_state =
+      record.mutable_next_stream_state();
+  *next_stream_state->mutable_stream_data() = MakeStreamData();
+  *next_stream_state->add_content() = MakeContent(0);
+  *next_stream_state->add_shared_state() = MakeSharedState(0);
+
+  MakeFeedStore({{"N", record}});
+
+  // Successful read
+  bool did_successful_read = false;
+  store_->ReadNextStreamState(base::BindLambdaForTesting(
+      [&](std::unique_ptr<feedstore::StreamAndContentState> result) {
+        did_successful_read = true;
+        ASSERT_TRUE(result);
+        EXPECT_TRUE(result->has_stream_data());
+        EXPECT_EQ(result->content_size(), 1);
+        EXPECT_EQ(result->shared_state_size(), 1);
+      }));
+  fake_db_->GetCallback(true);
+  EXPECT_TRUE(did_successful_read);
+
+  // Failed read
+  bool did_failed_read = false;
+  store_->ReadNextStreamState(base::BindLambdaForTesting(
+      [&](std::unique_ptr<feedstore::StreamAndContentState> result) {
+        did_failed_read = true;
+        EXPECT_FALSE(result);
+      }));
+  fake_db_->GetCallback(false);
+  EXPECT_TRUE(did_failed_read);
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/feed_stream.cc b/chromium/components/feed/core/v2/feed_stream.cc
new file mode 100644
index 00000000000..fe1e13c33f6
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_stream.cc
@@ -0,0 +1,448 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_stream.h"
+
+#include <set>
+#include <string>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/time/clock.h"
+#include "base/time/tick_clock.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/proto/v2/ui.pb.h"
+#include "components/feed/core/shared_prefs/pref_names.h"
+#include "components/feed/core/v2/enums.h"
+#include "components/feed/core/v2/feed_network.h"
+#include "components/feed/core/v2/feed_store.h"
+#include "components/feed/core/v2/refresh_task_scheduler.h"
+#include "components/feed/core/v2/scheduling.h"
+#include "components/feed/core/v2/stream_model.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+#include "components/feed/core/v2/tasks/load_stream_task.h"
+#include "components/feed/core/v2/tasks/wait_for_store_initialize_task.h"
+#include "components/prefs/pref_service.h"
+
+namespace feed {
+
+// Tracks UI changes in |StreamModel| and forwards them to |SurfaceInterface|s.
+// TODO(harringtond): implement spinner slice.
+class FeedStream::SurfaceUpdater : public StreamModel::Observer {
+ public:
+  using ContentRevision = ContentRevision;
+  explicit SurfaceUpdater(const base::ObserverList<SurfaceInterface>* surfaces)
+      : surfaces_(surfaces) {}
+  ~SurfaceUpdater() override = default;
+  SurfaceUpdater(const SurfaceUpdater&) = delete;
+  SurfaceUpdater& operator=(const SurfaceUpdater&) = delete;
+
+  void SetModel(StreamModel* model) {
+    if (model_ == model)
+      return;
+    if (model_)
+      model_->SetObserver(nullptr);
+    model_ = model;
+    if (model_) {
+      model_->SetObserver(this);
+
+      const std::vector<ContentRevision>& content_list =
+          model_->GetContentList();
+      current_content_set_.insert(content_list.begin(), content_list.end());
+      for (SurfaceInterface& surface : *surfaces_) {
+        surface.StreamUpdate(GetUpdateForNewSurface(*model_));
+      }
+    }
+  }
+
+  // StreamModel::Observer.
+  void OnUiUpdate(const StreamModel::UiUpdate& update) override {
+    DCHECK(model_);  // The update comes from the model.
+
+    if (!update.content_list_changed)
+      return;
+    feedui::StreamUpdate stream_update;
+    const std::vector<ContentRevision>& content_list = model_->GetContentList();
+    for (ContentRevision content_revision : content_list) {
+      AddSliceUpdate(*model_, content_revision,
+                     current_content_set_.count(content_revision) == 0,
+                     &stream_update);
+    }
+    for (const StreamModel::UiUpdate::SharedStateInfo& info :
+         update.shared_states) {
+      if (info.updated)
+        AddSharedState(*model_, info.shared_state_id, &stream_update);
+    }
+
+    current_content_set_.clear();
+    current_content_set_.insert(content_list.begin(), content_list.end());
+
+    for (SurfaceInterface& surface : *surfaces_) {
+      surface.StreamUpdate(stream_update);
+    }
+  }
+
+  // Sends the initial stream state to a newly connected surface.
+  void SurfaceAdded(SurfaceInterface* surface) {
+    if (model_) {
+      surface->StreamUpdate(GetUpdateForNewSurface(*model_));
+    }
+  }
+
+  void LoadStreamFailed(LoadStreamStatus load_stream_status) {
+    auto zero_state_type = feedui::ZeroStateSlice::NO_CARDS_AVAILABLE;
+    switch (load_stream_status) {
+      case LoadStreamStatus::kProtoTranslationFailed:
+      case LoadStreamStatus::kNoResponseBody:
+      case LoadStreamStatus::kCannotLoadFromNetworkOffline:
+      case LoadStreamStatus::kCannotLoadFromNetworkThrottled:
+        zero_state_type = feedui::ZeroStateSlice::CANT_REFRESH;
+        break;
+      default:
+        break;
+    }
+    // Note that with multiple surface, it's possible that we send a zero-state
+    // to a single surface multiple times.
+    for (SurfaceInterface& surface : *surfaces_) {
+      SendZeroStateUpdate(zero_state_type, &surface);
+    }
+  }
+
+ private:
+  static std::string ToSliceId(ContentRevision content_revision) {
+    auto integer_value = content_revision.value();
+    return std::string(reinterpret_cast<char*>(&integer_value),
+                       sizeof(integer_value));
+  }
+
+  static feedui::StreamUpdate GetUpdateForNewSurface(const StreamModel& model) {
+    feedui::StreamUpdate result;
+    for (ContentRevision content_revision : model.GetContentList()) {
+      AddSliceUpdate(model, content_revision, /*is_content_new=*/true, &result);
+    }
+    for (std::string& id : model.GetSharedStateIds()) {
+      AddSharedState(model, id, &result);
+    }
+
+    return result;
+  }
+
+  static void SendZeroStateUpdate(feedui::ZeroStateSlice::Type zero_state_type,
+                                  SurfaceInterface* surface) {
+    feedui::StreamUpdate update;
+    feedui::Slice* slice = update.add_updated_slices()->mutable_slice();
+    slice->mutable_zero_state_slice()->set_type(zero_state_type);
+    slice->set_slice_id("zero-state");
+    surface->StreamUpdate(update);
+  }
+
+  static void AddSharedState(const StreamModel& model,
+                             const std::string& shared_state_id,
+                             feedui::StreamUpdate* stream_update) {
+    const std::string* shared_state_data =
+        model.FindSharedStateData(shared_state_id);
+    if (!shared_state_data)
+      return;
+    feedui::SharedState* added_shared_state =
+        stream_update->add_new_shared_states();
+    added_shared_state->set_id(shared_state_id);
+    added_shared_state->set_xsurface_shared_state(*shared_state_data);
+  }
+
+  static void AddSliceUpdate(const StreamModel& model,
+                             ContentRevision content_revision,
+                             bool is_content_new,
+                             feedui::StreamUpdate* stream_update) {
+    if (is_content_new) {
+      feedui::Slice* slice =
+          stream_update->add_updated_slices()->mutable_slice();
+      slice->set_slice_id(ToSliceId(content_revision));
+      const feedstore::Content* content = model.FindContent(content_revision);
+      DCHECK(content);
+      slice->mutable_xsurface_slice()->set_xsurface_frame(content->frame());
+    } else {
+      stream_update->add_updated_slices()->set_slice_id(
+          ToSliceId(content_revision));
+    }
+  }
+
+  // Owned by |FeedStream|.
+  // Warning!: Null when the model is not yet loaded.
+  StreamModel* model_ = nullptr;
+  const base::ObserverList<SurfaceInterface>* surfaces_;
+
+  std::set<ContentRevision> current_content_set_;
+};
+
+std::unique_ptr<StreamModelUpdateRequest>
+FeedStream::WireResponseTranslator::TranslateWireResponse(
+    feedwire::Response response,
+    base::TimeDelta response_time,
+    base::Time current_time) {
+  return ::feed::TranslateWireResponse(std::move(response), response_time,
+                                       current_time);
+}
+
+FeedStream::FeedStream(
+    RefreshTaskScheduler* refresh_task_scheduler,
+    EventObserver* stream_event_observer,
+    Delegate* delegate,
+    PrefService* profile_prefs,
+    FeedNetwork* feed_network,
+    FeedStore* feed_store,
+    const base::Clock* clock,
+    const base::TickClock* tick_clock,
+    scoped_refptr<base::SequencedTaskRunner> background_task_runner)
+    : refresh_task_scheduler_(refresh_task_scheduler),
+      stream_event_observer_(stream_event_observer),
+      delegate_(delegate),
+      profile_prefs_(profile_prefs),
+      feed_network_(feed_network),
+      store_(feed_store),
+      clock_(clock),
+      tick_clock_(tick_clock),
+      background_task_runner_(background_task_runner),
+      task_queue_(this),
+      user_classifier_(std::make_unique<UserClassifier>(profile_prefs, clock)),
+      request_throttler_(profile_prefs, clock) {
+  static WireResponseTranslator default_translator;
+  wire_response_translator_ = &default_translator;
+
+  surface_updater_ = std::make_unique<SurfaceUpdater>(&surfaces_);
+
+  // Inserting this task first ensures that |store_| is initialized before
+  // it is used.
+  task_queue_.AddTask(std::make_unique<WaitForStoreInitializeTask>(store_));
+}
+
+void FeedStream::InitializeScheduling() {
+  if (!IsArticlesListVisible()) {
+    refresh_task_scheduler_->Cancel();
+    return;
+  }
+
+  refresh_task_scheduler_->EnsureScheduled(
+      GetUserClassTriggerThreshold(GetUserClass(), TriggerType::kFixedTimer));
+}
+
+FeedStream::~FeedStream() = default;
+
+void FeedStream::TriggerStreamLoad() {
+  if (model_ || model_loading_in_progress_)
+    return;
+
+  // If we should not load the stream, abort and send a zero-state update.
+  if (!IsArticlesListVisible()) {
+    LoadStreamTaskComplete(LoadStreamTask::Result(
+        LoadStreamStatus::kLoadNotAllowedArticlesListHidden));
+    return;
+  }
+  if (!delegate_->IsEulaAccepted()) {
+    LoadStreamTaskComplete(LoadStreamTask::Result(
+        LoadStreamStatus::kLoadNotAllowedEulaNotAccepted));
+    return;
+  }
+
+  model_loading_in_progress_ = true;
+  task_queue_.AddTask(std::make_unique<LoadStreamTask>(
+      this, base::BindOnce(&FeedStream::LoadStreamTaskComplete,
+                           base::Unretained(this))));
+}
+
+void FeedStream::LoadStreamTaskComplete(LoadStreamTask::Result result) {
+  stream_event_observer_->OnLoadStream(result.load_from_store_status,
+                                       result.final_status);
+  DVLOG(1) << "LoadStreamTaskComplete load_from_store_status="
+           << result.load_from_store_status
+           << " final_status=" << result.final_status;
+  model_loading_in_progress_ = false;
+
+  // If loading failed, update surfaces with an appropriate zero-state error.
+  if (!model_) {
+    surface_updater_->LoadStreamFailed(result.final_status);
+  }
+}
+
+void FeedStream::AttachSurface(SurfaceInterface* surface) {
+  surfaces_.AddObserver(surface);
+  surface_updater_->SurfaceAdded(surface);
+  TriggerStreamLoad();
+}
+
+void FeedStream::DetachSurface(SurfaceInterface* surface) {
+  surfaces_.RemoveObserver(surface);
+}
+
+void FeedStream::SetArticlesListVisible(bool is_visible) {
+  profile_prefs_->SetBoolean(prefs::kArticlesListVisible, is_visible);
+}
+
+bool FeedStream::IsArticlesListVisible() {
+  return profile_prefs_->GetBoolean(prefs::kArticlesListVisible);
+}
+
+void FeedStream::ExecuteOperations(
+    std::vector<feedstore::DataOperation> operations) {
+  if (!model_) {
+    DLOG(ERROR) << "Calling ExecuteOperations before the model is loaded";
+    return;
+  }
+  return model_->ExecuteOperations(std::move(operations));
+}
+
+EphemeralChangeId FeedStream::CreateEphemeralChange(
+    std::vector<feedstore::DataOperation> operations) {
+  if (!model_) {
+    DLOG(ERROR) << "Calling CreateEphemeralChange before the model is loaded";
+    return {};
+  }
+  return model_->CreateEphemeralChange(std::move(operations));
+}
+
+bool FeedStream::CommitEphemeralChange(EphemeralChangeId id) {
+  if (!model_)
+    return false;
+  return model_->CommitEphemeralChange(id);
+}
+
+bool FeedStream::RejectEphemeralChange(EphemeralChangeId id) {
+  if (!model_)
+    return false;
+  return model_->RejectEphemeralChange(id);
+}
+
+UserClass FeedStream::GetUserClass() {
+  return user_classifier_->GetUserClass();
+}
+
+base::Time FeedStream::GetLastFetchTime() {
+  const base::Time fetch_time =
+      profile_prefs_->GetTime(feed::prefs::kLastFetchAttemptTime);
+  // Ignore impossible time values.
+  if (fetch_time > clock_->Now())
+    return base::Time();
+  return fetch_time;
+}
+
+void FeedStream::LoadModelForTesting(std::unique_ptr<StreamModel> model) {
+  LoadModel(std::move(model));
+}
+offline_pages::TaskQueue* FeedStream::GetTaskQueueForTesting() {
+  return &task_queue_;
+}
+
+void FeedStream::OnTaskQueueIsIdle() {
+  if (idle_callback_)
+    idle_callback_.Run();
+}
+
+void FeedStream::SetIdleCallbackForTesting(
+    base::RepeatingClosure idle_callback) {
+  idle_callback_ = idle_callback;
+}
+
+void FeedStream::SetUserClassifierForTesting(
+    std::unique_ptr<UserClassifier> user_classifier) {
+  user_classifier_ = std::move(user_classifier);
+}
+
+void FeedStream::OnStoreChange(const StreamModel::StoreUpdate& update) {
+  store_->WriteOperations(update.sequence_number, update.operations);
+}
+
+LoadStreamStatus FeedStream::ShouldMakeFeedQueryRequest() {
+  // TODO(harringtond): |suppress_refreshes_until_| was historically used for
+  // privacy purposes after clearing data to make sure sync data made it to the
+  // server. I'm not sure we need this now. But also, it was documented as not
+  // affecting manually triggered refreshes, but coded in a way that it does.
+  // I've tried to keep the same functionality as the old feed code, but we
+  // should revisit this.
+  if (tick_clock_->NowTicks() < suppress_refreshes_until_) {
+    return LoadStreamStatus::kCannotLoadFromNetworkSupressedForHistoryDelete;
+  }
+
+  if (delegate_->IsOffline()) {
+    return LoadStreamStatus::kCannotLoadFromNetworkOffline;
+  }
+
+  if (!request_throttler_.RequestQuota(NetworkRequestType::kFeedQuery)) {
+    return LoadStreamStatus::kCannotLoadFromNetworkThrottled;
+  }
+
+  return LoadStreamStatus::kNoStatus;
+}
+
+void FeedStream::OnEulaAccepted() {
+  MaybeTriggerRefresh(TriggerType::kForegrounded);
+}
+
+void FeedStream::OnHistoryDeleted() {
+  // Due to privacy, we should not fetch for a while (unless the user
+  // explicitly asks for new suggestions) to give sync the time to propagate
+  // the changes in history to the server.
+  suppress_refreshes_until_ =
+      tick_clock_->NowTicks() + kSuppressRefreshDuration;
+  ClearAll();
+}
+
+void FeedStream::OnCacheDataCleared() {
+  ClearAll();
+}
+
+void FeedStream::OnSignedIn() {
+  ClearAll();
+}
+
+void FeedStream::OnSignedOut() {
+  ClearAll();
+}
+
+void FeedStream::OnEnterForeground() {
+  MaybeTriggerRefresh(TriggerType::kForegrounded);
+}
+
+void FeedStream::ExecuteRefreshTask() {
+  if (!IsArticlesListVisible()) {
+    // While the check and cancel isn't strictly necessary, a long lived session
+    // could be issuing refreshes due to the background trigger while articles
+    // are not visible.
+    refresh_task_scheduler_->Cancel();
+    return;
+  }
+  MaybeTriggerRefresh(TriggerType::kFixedTimer);
+}
+
+void FeedStream::ClearAll() {
+  // TODO(harringtond): How should we handle in-progress tasks.
+  stream_event_observer_->OnClearAll(clock_->Now() - GetLastFetchTime());
+
+  // TODO(harringtond): This should result in clearing feed data
+  // and _maybe_ triggering refresh with TriggerType::kNtpShown.
+  // That work should be embedded in a task.
+}
+
+void FeedStream::MaybeTriggerRefresh(TriggerType trigger,
+                                     bool clear_all_before_refresh) {
+  stream_event_observer_->OnMaybeTriggerRefresh(trigger,
+                                                clear_all_before_refresh);
+  // TODO(harringtond): Implement refresh (with LoadStreamTask).
+}
+
+void FeedStream::LoadModel(std::unique_ptr<StreamModel> model) {
+  DCHECK(!model_);
+  model_ = std::move(model);
+  model_->SetStoreObserver(this);
+  surface_updater_->SetModel(model_.get());
+}
+
+void FeedStream::UnloadModel() {
+  if (!model_)
+    return;
+  surface_updater_->SetModel(nullptr);
+  model_.reset();
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/feed_stream.h b/chromium/components/feed/core/v2/feed_stream.h
new file mode 100644
index 00000000000..5c636822809
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_stream.h
@@ -0,0 +1,225 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_FEED_STREAM_H_
+#define COMPONENTS_FEED_CORE_V2_FEED_STREAM_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/memory/scoped_refptr.h"
+#include "base/observer_list.h"
+#include "base/sequenced_task_runner.h"
+#include "base/task_runner_util.h"
+#include "components/feed/core/common/enums.h"
+#include "components/feed/core/common/user_classifier.h"
+#include "components/feed/core/proto/v2/wire/response.pb.h"
+#include "components/feed/core/v2/enums.h"
+#include "components/feed/core/v2/public/feed_stream_api.h"
+#include "components/feed/core/v2/request_throttler.h"
+#include "components/feed/core/v2/stream_model.h"
+#include "components/feed/core/v2/tasks/load_stream_task.h"
+#include "components/offline_pages/task/task_queue.h"
+
+class PrefService;
+
+namespace base {
+class Clock;
+class TickClock;
+}  // namespace base
+
+namespace feed {
+class FeedStore;
+class StreamModel;
+class FeedNetwork;
+class RefreshTaskScheduler;
+struct StreamModelUpdateRequest;
+
+// Implements FeedStreamApi. |FeedStream| additionally exposes functionality
+// needed by other classes within the Feed component.
+class FeedStream : public FeedStreamApi,
+                   public offline_pages::TaskQueue::Delegate,
+                   public StreamModel::StoreObserver {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() = default;
+    // Returns true if Chrome's EULA has been accepted.
+    virtual bool IsEulaAccepted() = 0;
+    // Returns true if the device is offline.
+    virtual bool IsOffline() = 0;
+  };
+
+  // An observer of stream events for testing and for tracking metrics.
+  // Concrete implementation should have no observable effects on the Feed.
+  class EventObserver {
+   public:
+    virtual void OnLoadStream(LoadStreamStatus load_from_store_status,
+                              LoadStreamStatus final_status) = 0;
+    virtual void OnMaybeTriggerRefresh(TriggerType trigger,
+                                       bool clear_all_before_refresh) = 0;
+    virtual void OnClearAll(base::TimeDelta time_since_last_clear) = 0;
+  };
+
+  // Forwards to |feed::TranslateWireResponse()| by default. Can be overridden
+  // for testing.
+  class WireResponseTranslator {
+   public:
+    WireResponseTranslator() = default;
+    ~WireResponseTranslator() = default;
+    virtual std::unique_ptr<StreamModelUpdateRequest> TranslateWireResponse(
+        feedwire::Response response,
+        base::TimeDelta response_time,
+        base::Time current_time);
+  };
+
+  FeedStream(RefreshTaskScheduler* refresh_task_scheduler,
+             EventObserver* stream_event_observer,
+             Delegate* delegate,
+             PrefService* profile_prefs,
+             FeedNetwork* feed_network,
+             FeedStore* feed_store,
+             const base::Clock* clock,
+             const base::TickClock* tick_clock,
+             scoped_refptr<base::SequencedTaskRunner> background_task_runner);
+  ~FeedStream() override;
+
+  FeedStream(const FeedStream&) = delete;
+  FeedStream& operator=(const FeedStream&) = delete;
+
+  // Initializes scheduling. This should be called at startup.
+  void InitializeScheduling();
+
+  // FeedStreamApi.
+
+  void AttachSurface(SurfaceInterface*) override;
+  void DetachSurface(SurfaceInterface*) override;
+  void SetArticlesListVisible(bool is_visible) override;
+  bool IsArticlesListVisible() override;
+  void ExecuteOperations(
+      std::vector<feedstore::DataOperation> operations) override;
+  EphemeralChangeId CreateEphemeralChange(
+      std::vector<feedstore::DataOperation> operations) override;
+  bool CommitEphemeralChange(EphemeralChangeId id) override;
+  bool RejectEphemeralChange(EphemeralChangeId id) override;
+
+  // offline_pages::TaskQueue::Delegate.
+  void OnTaskQueueIsIdle() override;
+
+  // StreamModel::StoreObserver.
+  void OnStoreChange(const StreamModel::StoreUpdate& update) override;
+
+  // Event indicators. These functions are called from an external source
+  // to indicate an event.
+
+  // Called when Chrome's EULA has been accepted. This should happen when
+  // Delegate::IsEulaAccepted() changes from false to true.
+  void OnEulaAccepted();
+  // Invoked when Chrome is foregrounded.
+  void OnEnterForeground();
+  // The user signed in to Chrome.
+  void OnSignedIn();
+  // The user signed out of Chrome.
+  void OnSignedOut();
+  // The user has deleted their Chrome history.
+  void OnHistoryDeleted();
+  // Chrome's cached data was cleared.
+  void OnCacheDataCleared();
+  // Invoked by RefreshTaskScheduler's scheduled task.
+  void ExecuteRefreshTask();
+
+  // State shared for the sake of implementing FeedStream. Typically these
+  // functions are used by tasks.
+
+  void LoadModel(std::unique_ptr<StreamModel> model);
+
+  FeedNetwork* GetNetwork() { return feed_network_; }
+  FeedStore* GetStore() { return store_; }
+
+  // Returns the computed UserClass for the active user.
+  UserClass GetUserClass();
+
+  // Returns the time of the last content fetch.
+  base::Time GetLastFetchTime();
+
+  // Determines if a FeedQuery request can be made. If successful,
+  // returns |LoadStreamStatus::kNoStatus| and acquires throttler quota.
+  // Otherwise returns the reason.
+  LoadStreamStatus ShouldMakeFeedQueryRequest();
+
+  // Loads |model|. Should be used for testing in place of typical model
+  // loading from network or storage.
+  void LoadModelForTesting(std::unique_ptr<StreamModel> model);
+  offline_pages::TaskQueue* GetTaskQueueForTesting();
+  void UnloadModelForTesting() { UnloadModel(); }
+
+  // Returns the model if it is loaded, or null otherwise.
+  StreamModel* GetModel() { return model_.get(); }
+
+  const base::Clock* GetClock() { return clock_; }
+
+  WireResponseTranslator* GetWireResponseTranslator() const {
+    return wire_response_translator_;
+  }
+
+  void SetWireResponseTranslatorForTesting(
+      WireResponseTranslator* wire_response_translator) {
+    wire_response_translator_ = wire_response_translator;
+  }
+
+  void SetIdleCallbackForTesting(base::RepeatingClosure idle_callback);
+  void SetUserClassifierForTesting(
+      std::unique_ptr<UserClassifier> user_classifier);
+
+ private:
+  class SurfaceUpdater;
+  class ModelStoreChangeMonitor;
+  void MaybeTriggerRefresh(TriggerType trigger,
+                           bool clear_all_before_refresh = false);
+  void TriggerStreamLoad();
+  void UnloadModel();
+
+  void LoadStreamTaskComplete(LoadStreamTask::Result result);
+
+  void ClearAll();
+
+  // Unowned.
+
+  RefreshTaskScheduler* refresh_task_scheduler_;
+  EventObserver* stream_event_observer_;
+  Delegate* delegate_;
+  PrefService* profile_prefs_;
+  FeedNetwork* feed_network_;
+  FeedStore* store_;
+  const base::Clock* clock_;
+  const base::TickClock* tick_clock_;
+  WireResponseTranslator* wire_response_translator_;
+
+  scoped_refptr<base::SequencedTaskRunner> background_task_runner_;
+
+  offline_pages::TaskQueue task_queue_;
+  // Whether the model is being loaded. Used to prevent multiple simultaneous
+  // attempts to load the model.
+  bool model_loading_in_progress_ = false;
+  std::unique_ptr<SurfaceUpdater> surface_updater_;
+  // The stream model. Null if not yet loaded.
+  // Internally, this should only be changed by |LoadModel()| and
+  // |UnloadModel()|.
+  std::unique_ptr<StreamModel> model_;
+
+  // Set of (unowned) attached surfaces.
+  base::ObserverList<SurfaceInterface> surfaces_;
+
+  // Mutable state.
+  std::unique_ptr<UserClassifier> user_classifier_;
+  RequestThrottler request_throttler_;
+  base::TimeTicks suppress_refreshes_until_;
+
+  // To allow tests to wait on task queue idle.
+  base::RepeatingClosure idle_callback_;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_FEED_STREAM_H_
diff --git a/chromium/components/feed/core/v2/feed_stream_unittest.cc b/chromium/components/feed/core/v2/feed_stream_unittest.cc
new file mode 100644
index 00000000000..a514fd7cc63
--- /dev/null
+++ b/chromium/components/feed/core/v2/feed_stream_unittest.cc
@@ -0,0 +1,713 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/feed_stream.h"
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "base/optional.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/test/bind_test_util.h"
+#include "base/test/scoped_run_loop_timeout.h"
+#include "base/test/simple_test_clock.h"
+#include "base/test/simple_test_tick_clock.h"
+#include "base/test/task_environment.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/proto/v2/ui.pb.h"
+#include "components/feed/core/proto/v2/wire/request.pb.h"
+#include "components/feed/core/shared_prefs/pref_names.h"
+#include "components/feed/core/v2/feed_network.h"
+#include "components/feed/core/v2/refresh_task_scheduler.h"
+#include "components/feed/core/v2/scheduling.h"
+#include "components/feed/core/v2/stream_model.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+#include "components/feed/core/v2/tasks/load_stream_from_store_task.h"
+#include "components/feed/core/v2/test/stream_builder.h"
+#include "components/leveldb_proto/public/proto_database_provider.h"
+#include "components/prefs/pref_registry_simple.h"
+#include "components/prefs/testing_pref_service.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace feed {
+namespace {
+
+std::unique_ptr<StreamModel> LoadModelFromStore(FeedStore* store) {
+  LoadStreamFromStoreTask::Result result;
+  auto complete = [&](LoadStreamFromStoreTask::Result task_result) {
+    result = std::move(task_result);
+  };
+  LoadStreamFromStoreTask load_task(
+      store, /*clock=*/nullptr,
+      UserClass::kActiveSuggestionsConsumer,  // Has no effect.
+      base::BindLambdaForTesting(complete));
+  // We want to load the data no matter how stale.
+  load_task.IgnoreStalenessForTesting();
+
+  base::RunLoop run_loop;
+  load_task.Execute(run_loop.QuitClosure());
+  run_loop.Run();
+
+  if (result.status == LoadStreamStatus::kLoadedFromStore) {
+    auto model = std::make_unique<StreamModel>();
+    model->Update(std::move(result.update_request));
+    return model;
+  }
+  LOG(WARNING) << "LoadModelFromStore failed with " << result.status;
+  return nullptr;
+}
+
+// Returns the model state string (|StreamModel::DumpStateForTesting()|),
+// given a model initialized with |update_request| and having |operations|
+// applied.
+std::string ModelStateFor(
+    std::unique_ptr<StreamModelUpdateRequest> update_request,
+    std::vector<feedstore::DataOperation> operations = {},
+    std::vector<feedstore::DataOperation> more_operations = {}) {
+  StreamModel model;
+  model.Update(std::move(update_request));
+  model.ExecuteOperations(operations);
+  model.ExecuteOperations(more_operations);
+  return model.DumpStateForTesting();
+}
+
+// Returns the model state string (|StreamModel::DumpStateForTesting()|),
+// given a model initialized with |store|.
+std::string ModelStateFor(FeedStore* store) {
+  auto model = LoadModelFromStore(store);
+  if (model) {
+    return model->DumpStateForTesting();
+  }
+  return "{Failed to load model from store}";
+}
+
+// This is EXPECT_EQ, but also dumps the string values for ease of reading.
+#define EXPECT_STRINGS_EQUAL(WANT, GOT)                                       \
+  {                                                                           \
+    std::string want = (WANT), got = (GOT);                                   \
+    EXPECT_EQ(want, got) << "Wanted:\n" << (want) << "\nBut got:\n" << (got); \
+  }
+
+class TestSurface : public FeedStream::SurfaceInterface {
+ public:
+  // FeedStream::SurfaceInterface.
+  void StreamUpdate(const feedui::StreamUpdate& stream_update) override {
+    if (!initial_state)
+      initial_state = stream_update;
+    update = stream_update;
+    ++update_count_;
+  }
+
+  // Test functions.
+
+  void Clear() {
+    initial_state = base::nullopt;
+    update = base::nullopt;
+    update_count_ = 0;
+  }
+
+  // Describe what is shown on the surface in a format that can be easily
+  // asserted against.
+  std::string Describe() {
+    if (!initial_state)
+      return "empty";
+
+    if (update->updated_slices().size() == 1 &&
+        update->updated_slices()[0].has_slice() &&
+        update->updated_slices()[0].slice().has_zero_state_slice()) {
+      return "zero-state";
+    }
+
+    std::stringstream ss;
+    ss << update->updated_slices().size() << " slices";
+    // If there's more than one update, we want to know that.
+    if (update_count_ > 1) {
+      ss << " " << update_count_ << " updates";
+    }
+    return ss.str();
+  }
+
+  base::Optional<feedui::StreamUpdate> initial_state;
+  base::Optional<feedui::StreamUpdate> update;
+
+ private:
+  int update_count_ = 0;
+};
+
+class TestUserClassifier : public UserClassifier {
+ public:
+  TestUserClassifier(PrefService* pref_service, const base::Clock* clock)
+      : UserClassifier(pref_service, clock) {}
+  // UserClassifier.
+  UserClass GetUserClass() const override {
+    return overridden_user_class_.value_or(UserClassifier::GetUserClass());
+  }
+
+  // Test use.
+  void OverrideUserClass(UserClass user_class) {
+    overridden_user_class_ = user_class;
+  }
+
+ private:
+  base::Optional<UserClass> overridden_user_class_;
+};
+
+class TestFeedNetwork : public FeedNetwork {
+ public:
+  // FeedNetwork implementation.
+  void SendQueryRequest(
+      const feedwire::Request& request,
+      base::OnceCallback<void(QueryRequestResult)> callback) override {
+    ++send_query_call_count;
+    // Emulate a successful response.
+    // The response body is currently an empty message, because most of the
+    // time we want to inject a translated response for ease of test-writing.
+    query_request_sent = request;
+    QueryRequestResult result;
+    result.status_code = 200;
+    result.response_body = std::make_unique<feedwire::Response>();
+    base::SequencedTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::BindOnce(std::move(callback), std::move(result)));
+  }
+  void SendActionRequest(
+      const feedwire::ActionRequest& request,
+      base::OnceCallback<void(ActionRequestResult)> callback) override {
+    NOTIMPLEMENTED();
+  }
+  void CancelRequests() override { NOTIMPLEMENTED(); }
+
+  base::Optional<feedwire::Request> query_request_sent;
+  int send_query_call_count = 0;
+};
+
+// Forwards to |FeedStream::WireResponseTranslator| unless a response is
+// injected.
+class TestWireResponseTranslator : public FeedStream::WireResponseTranslator {
+ public:
+  std::unique_ptr<StreamModelUpdateRequest> TranslateWireResponse(
+      feedwire::Response response,
+      base::TimeDelta response_time,
+      base::Time current_time) override {
+    if (injected_response_) {
+      return std::move(injected_response_);
+    }
+    return FeedStream::WireResponseTranslator::TranslateWireResponse(
+        std::move(response), response_time, current_time);
+  }
+  void InjectResponse(std::unique_ptr<StreamModelUpdateRequest> response) {
+    injected_response_ = std::move(response);
+  }
+  bool InjectedResponseConsumed() const { return !injected_response_; }
+
+ private:
+  std::unique_ptr<StreamModelUpdateRequest> injected_response_;
+};
+
+class FakeRefreshTaskScheduler : public RefreshTaskScheduler {
+ public:
+  // RefreshTaskScheduler implementation.
+  void EnsureScheduled(base::TimeDelta period) override {
+    scheduled_period = period;
+  }
+  void Cancel() override { canceled = true; }
+  void RefreshTaskComplete() override { refresh_task_complete = true; }
+
+  base::Optional<base::TimeDelta> scheduled_period;
+  bool canceled = false;
+  bool refresh_task_complete = false;
+};
+
+class TestEventObserver : public FeedStream::EventObserver {
+ public:
+  // FeedStreamUnittest::StreamEventObserver.
+  void OnLoadStream(LoadStreamStatus load_from_store_status,
+                    LoadStreamStatus final_status) override {
+    load_stream_status = final_status;
+    LOG(INFO) << "OnLoadStream: " << final_status
+              << " (store status: " << load_from_store_status << ")";
+  }
+  void OnMaybeTriggerRefresh(TriggerType trigger,
+                             bool clear_all_before_refresh) override {
+    refresh_trigger_type = trigger;
+  }
+  void OnClearAll(base::TimeDelta time_since_last_clear) override {
+    this->time_since_last_clear = time_since_last_clear;
+  }
+
+  // Test access.
+
+  base::Optional<LoadStreamStatus> load_stream_status;
+  base::Optional<base::TimeDelta> time_since_last_clear;
+  base::Optional<TriggerType> refresh_trigger_type;
+};
+
+class FeedStreamTest : public testing::Test, public FeedStream::Delegate {
+ public:
+  void SetUp() override {
+    feed::prefs::RegisterFeedSharedProfilePrefs(profile_prefs_.registry());
+    feed::RegisterProfilePrefs(profile_prefs_.registry());
+    CHECK_EQ(kTestTimeEpoch, task_environment_.GetMockClock()->Now());
+    stream_ = std::make_unique<FeedStream>(
+        &refresh_scheduler_, &event_observer_, this, &profile_prefs_, &network_,
+        store_.get(), task_environment_.GetMockClock(),
+        task_environment_.GetMockTickClock(),
+        task_environment_.GetMainThreadTaskRunner());
+
+    // Set the user classifier.
+    auto user_classifier = std::make_unique<TestUserClassifier>(
+        &profile_prefs_, task_environment_.GetMockClock());
+    user_classifier_ = user_classifier.get();
+    stream_->SetUserClassifierForTesting(std::move(user_classifier));
+
+    WaitForIdleTaskQueue();  // Wait for any initialization.
+
+    stream_->SetWireResponseTranslatorForTesting(&response_translator_);
+  }
+
+  void TearDown() override {
+    // Ensure the task queue can return to idle. Failure to do so may be due
+    // to a stuck task that never called |TaskComplete()|.
+    WaitForIdleTaskQueue();
+    // Store requires PostTask to clean up.
+    store_.reset();
+    task_environment_.RunUntilIdle();
+  }
+
+  // FeedStream::Delegate.
+  bool IsEulaAccepted() override { return is_eula_accepted_; }
+  bool IsOffline() override { return is_offline_; }
+
+  // For tests.
+
+  bool IsTaskQueueIdle() const {
+    return !stream_->GetTaskQueueForTesting()->HasPendingTasks() &&
+           !stream_->GetTaskQueueForTesting()->HasRunningTask();
+  }
+
+  void WaitForIdleTaskQueue() {
+    if (IsTaskQueueIdle())
+      return;
+    base::test::ScopedRunLoopTimeout run_timeout(
+        FROM_HERE, base::TimeDelta::FromSeconds(1));
+    base::RunLoop run_loop;
+    stream_->SetIdleCallbackForTesting(run_loop.QuitClosure());
+    run_loop.Run();
+  }
+
+  void UnloadModel() {
+    WaitForIdleTaskQueue();
+    stream_->UnloadModelForTesting();
+  }
+
+ protected:
+  base::test::TaskEnvironment task_environment_{
+      base::test::TaskEnvironment::TimeSource::MOCK_TIME};
+  TestUserClassifier* user_classifier_;
+  TestEventObserver event_observer_;
+  TestingPrefServiceSimple profile_prefs_;
+  TestFeedNetwork network_;
+  TestWireResponseTranslator response_translator_;
+
+  std::unique_ptr<FeedStore> store_ = std::make_unique<FeedStore>(
+      leveldb_proto::ProtoDatabaseProvider::GetUniqueDB<feedstore::Record>(
+          leveldb_proto::ProtoDbType::FEED_STREAM_DATABASE,
+          /*file_path=*/{},
+          task_environment_.GetMainThreadTaskRunner()));
+  FakeRefreshTaskScheduler refresh_scheduler_;
+  std::unique_ptr<FeedStream> stream_;
+  bool is_eula_accepted_ = true;
+  bool is_offline_ = false;
+};
+
+TEST_F(FeedStreamTest, IsArticlesListVisibleByDefault) {
+  EXPECT_TRUE(stream_->IsArticlesListVisible());
+}
+
+TEST_F(FeedStreamTest, SetArticlesListVisible) {
+  EXPECT_TRUE(stream_->IsArticlesListVisible());
+  stream_->SetArticlesListVisible(false);
+  EXPECT_FALSE(stream_->IsArticlesListVisible());
+  stream_->SetArticlesListVisible(true);
+  EXPECT_TRUE(stream_->IsArticlesListVisible());
+}
+
+TEST_F(FeedStreamTest, RefreshIsScheduledOnInitialize) {
+  stream_->InitializeScheduling();
+  EXPECT_TRUE(refresh_scheduler_.scheduled_period);
+}
+
+TEST_F(FeedStreamTest, ScheduledRefreshTriggersRefresh) {
+  stream_->InitializeScheduling();
+  stream_->ExecuteRefreshTask();
+
+  EXPECT_EQ(TriggerType::kFixedTimer, event_observer_.refresh_trigger_type);
+  // TODO(harringtond): Once we actually perform the refresh, make sure
+  // RefreshTaskComplete() is called.
+  // EXPECT_TRUE(refresh_scheduler_.refresh_task_complete);
+}
+
+TEST_F(FeedStreamTest, DoNotRefreshIfArticlesListIsHidden) {
+  stream_->SetArticlesListVisible(false);
+  stream_->InitializeScheduling();
+  stream_->ExecuteRefreshTask();
+
+  EXPECT_TRUE(refresh_scheduler_.canceled);
+  EXPECT_FALSE(event_observer_.refresh_trigger_type);
+}
+
+TEST_F(FeedStreamTest, SurfaceReceivesInitialContent) {
+  {
+    auto model = std::make_unique<StreamModel>();
+    model->Update(MakeTypicalInitialModelState());
+    stream_->LoadModelForTesting(std::move(model));
+  }
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  ASSERT_TRUE(surface.initial_state);
+  const feedui::StreamUpdate& initial_state = surface.initial_state.value();
+  ASSERT_EQ(2, initial_state.updated_slices().size());
+  EXPECT_NE("", initial_state.updated_slices(0).slice().slice_id());
+  EXPECT_EQ("f:0", initial_state.updated_slices(0)
+                       .slice()
+                       .xsurface_slice()
+                       .xsurface_frame());
+  EXPECT_NE("", initial_state.updated_slices(1).slice().slice_id());
+  EXPECT_EQ("f:1", initial_state.updated_slices(1)
+                       .slice()
+                       .xsurface_slice()
+                       .xsurface_frame());
+  ASSERT_EQ(1, initial_state.new_shared_states().size());
+  EXPECT_EQ("ss:0",
+            initial_state.new_shared_states()[0].xsurface_shared_state());
+}
+
+TEST_F(FeedStreamTest, SurfaceReceivesInitialContentLoadedAfterAttach) {
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  ASSERT_FALSE(surface.initial_state);
+  {
+    auto model = std::make_unique<StreamModel>();
+    model->Update(MakeTypicalInitialModelState());
+    stream_->LoadModelForTesting(std::move(model));
+  }
+
+  ASSERT_EQ("2 slices", surface.Describe());
+  const feedui::StreamUpdate& initial_state = surface.initial_state.value();
+
+  EXPECT_NE("", initial_state.updated_slices(0).slice().slice_id());
+  EXPECT_EQ("f:0", initial_state.updated_slices(0)
+                       .slice()
+                       .xsurface_slice()
+                       .xsurface_frame());
+  EXPECT_NE("", initial_state.updated_slices(1).slice().slice_id());
+  EXPECT_EQ("f:1", initial_state.updated_slices(1)
+                       .slice()
+                       .xsurface_slice()
+                       .xsurface_frame());
+  ASSERT_EQ(1, initial_state.new_shared_states().size());
+  EXPECT_EQ("ss:0",
+            initial_state.new_shared_states()[0].xsurface_shared_state());
+}
+
+TEST_F(FeedStreamTest, SurfaceReceivesUpdatedContent) {
+  {
+    auto model = std::make_unique<StreamModel>();
+    model->ExecuteOperations(MakeTypicalStreamOperations());
+    stream_->LoadModelForTesting(std::move(model));
+  }
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  // Remove #1, add #2.
+  stream_->ExecuteOperations({
+      MakeOperation(MakeRemove(MakeClusterId(1))),
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  });
+  ASSERT_TRUE(surface.update);
+  const feedui::StreamUpdate& initial_state = surface.initial_state.value();
+  const feedui::StreamUpdate& update = surface.update.value();
+
+  ASSERT_EQ("2 slices 2 updates", surface.Describe());
+  // First slice is just an ID that matches the old 1st slice ID.
+  EXPECT_EQ(initial_state.updated_slices(0).slice().slice_id(),
+            update.updated_slices(0).slice_id());
+  // Second slice is a new xsurface slice.
+  EXPECT_NE("", update.updated_slices(1).slice().slice_id());
+  EXPECT_EQ("f:2",
+            update.updated_slices(1).slice().xsurface_slice().xsurface_frame());
+}
+
+TEST_F(FeedStreamTest, SurfaceReceivesSecondUpdatedContent) {
+  {
+    auto model = std::make_unique<StreamModel>();
+    model->ExecuteOperations(MakeTypicalStreamOperations());
+    stream_->LoadModelForTesting(std::move(model));
+  }
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  // Add #2.
+  stream_->ExecuteOperations({
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  });
+
+  // Clear the last update and add #3.
+  stream_->ExecuteOperations({
+      MakeOperation(MakeCluster(3, MakeRootId())),
+      MakeOperation(MakeContentNode(3, MakeClusterId(3))),
+      MakeOperation(MakeContent(3)),
+  });
+
+  // The last update should have only one new piece of content.
+  // This verifies the current content set is tracked properly.
+  ASSERT_EQ("4 slices 3 updates", surface.Describe());
+
+  ASSERT_EQ(4, surface.update->updated_slices().size());
+  EXPECT_FALSE(surface.update->updated_slices(0).has_slice());
+  EXPECT_FALSE(surface.update->updated_slices(1).has_slice());
+  EXPECT_FALSE(surface.update->updated_slices(2).has_slice());
+  EXPECT_EQ("f:3", surface.update->updated_slices(3)
+                       .slice()
+                       .xsurface_slice()
+                       .xsurface_frame());
+}
+
+TEST_F(FeedStreamTest, DetachSurface) {
+  {
+    auto model = std::make_unique<StreamModel>();
+    model->ExecuteOperations(MakeTypicalStreamOperations());
+    stream_->LoadModelForTesting(std::move(model));
+  }
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  EXPECT_TRUE(surface.initial_state);
+  stream_->DetachSurface(&surface);
+  surface.Clear();
+
+  // Arbitrary stream change. Surface should not see the update.
+  stream_->ExecuteOperations({
+      MakeOperation(MakeRemove(MakeClusterId(1))),
+  });
+  EXPECT_FALSE(surface.update);
+}
+
+TEST_F(FeedStreamTest, LoadFromNetwork) {
+  // Store is empty, so we should fallback to a network request.
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_TRUE(network_.query_request_sent);
+  EXPECT_TRUE(response_translator_.InjectedResponseConsumed());
+  EXPECT_EQ("2 slices", surface.Describe());
+  // Verify the model is filled correctly.
+  EXPECT_STRINGS_EQUAL(ModelStateFor(MakeTypicalInitialModelState()),
+                       stream_->GetModel()->DumpStateForTesting());
+  // Verify the data was written to the store.
+  EXPECT_STRINGS_EQUAL(ModelStateFor(store_.get()),
+                       ModelStateFor(MakeTypicalInitialModelState()));
+}
+
+TEST_F(FeedStreamTest, LoadFromNetworkBecauseStoreIsStale) {
+  // Fill the store with stream data that is just barely stale, and verify we
+  // fetch new data over the network.
+  user_classifier_->OverrideUserClass(UserClass::kActiveSuggestionsConsumer);
+  store_->SaveFullStream(MakeTypicalInitialModelState(
+
+                             kTestTimeEpoch - base::TimeDelta::FromHours(12) -
+                             base::TimeDelta::FromMinutes(1)),
+                         base::DoNothing());
+
+  // Store is stale, so we should fallback to a network request.
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_TRUE(network_.query_request_sent);
+  EXPECT_TRUE(response_translator_.InjectedResponseConsumed());
+  ASSERT_TRUE(surface.initial_state);
+}
+
+TEST_F(FeedStreamTest, LoadFromNetworkFailsDueToProtoTranslation) {
+  // No data in the store, so we should fetch from the network.
+  // The network will respond with an empty response, which should fail proto
+  // translation.
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ(LoadStreamStatus::kProtoTranslationFailed,
+            event_observer_.load_stream_status);
+}
+
+TEST_F(FeedStreamTest, DoNotLoadFromNetworkWhenOffline) {
+  is_offline_ = true;
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ(LoadStreamStatus::kCannotLoadFromNetworkOffline,
+            event_observer_.load_stream_status);
+  EXPECT_EQ("zero-state", surface.Describe());
+}
+
+TEST_F(FeedStreamTest, DoNotLoadStreamWhenArticleListIsHidden) {
+  stream_->SetArticlesListVisible(false);
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ(LoadStreamStatus::kLoadNotAllowedArticlesListHidden,
+            event_observer_.load_stream_status);
+  EXPECT_EQ("zero-state", surface.Describe());
+}
+
+TEST_F(FeedStreamTest, DoNotLoadStreamWhenEulaIsNotAccepted) {
+  is_eula_accepted_ = false;
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ(LoadStreamStatus::kLoadNotAllowedEulaNotAccepted,
+            event_observer_.load_stream_status);
+  EXPECT_EQ("zero-state", surface.Describe());
+}
+
+TEST_F(FeedStreamTest, DoNotLoadFromNetworkAfterHistoryIsDeleted) {
+  stream_->OnHistoryDeleted();
+  task_environment_.FastForwardBy(kSuppressRefreshDuration -
+                                  base::TimeDelta::FromSeconds(1));
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ("zero-state", surface.Describe());
+
+  EXPECT_EQ(LoadStreamStatus::kCannotLoadFromNetworkSupressedForHistoryDelete,
+            event_observer_.load_stream_status);
+
+  stream_->DetachSurface(&surface);
+  task_environment_.FastForwardBy(base::TimeDelta::FromSeconds(2));
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ("2 slices 2 updates", surface.Describe());
+}
+
+TEST_F(FeedStreamTest, ShouldMakeFeedQueryRequestConsumesQuota) {
+  LoadStreamStatus status = LoadStreamStatus::kNoStatus;
+  for (; status == LoadStreamStatus::kNoStatus;
+       status = stream_->ShouldMakeFeedQueryRequest()) {
+  }
+
+  ASSERT_EQ(LoadStreamStatus::kCannotLoadFromNetworkThrottled, status);
+}
+
+TEST_F(FeedStreamTest, LoadStreamFromStore) {
+  // Fill the store with stream data that is just barely fresh, and verify it
+  // loads.
+  user_classifier_->OverrideUserClass(UserClass::kActiveSuggestionsConsumer);
+  store_->SaveFullStream(MakeTypicalInitialModelState(
+                             kTestTimeEpoch - base::TimeDelta::FromHours(12) +
+                             base::TimeDelta::FromMinutes(1)),
+                         base::DoNothing());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  ASSERT_EQ("2 slices", surface.Describe());
+  EXPECT_FALSE(network_.query_request_sent);
+  // Verify the model is filled correctly.
+  EXPECT_STRINGS_EQUAL(ModelStateFor(MakeTypicalInitialModelState()),
+                       stream_->GetModel()->DumpStateForTesting());
+}
+
+TEST_F(FeedStreamTest, DetachSurfaceWhileLoadingModel) {
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  stream_->DetachSurface(&surface);
+  WaitForIdleTaskQueue();
+
+  EXPECT_EQ("empty", surface.Describe());
+  EXPECT_TRUE(network_.query_request_sent);
+}
+
+TEST_F(FeedStreamTest, AttachMultipleSurfacesLoadsModelOnce) {
+  response_translator_.InjectResponse(MakeTypicalInitialModelState());
+  TestSurface surface;
+  TestSurface other_surface;
+  stream_->AttachSurface(&surface);
+  stream_->AttachSurface(&other_surface);
+  WaitForIdleTaskQueue();
+
+  ASSERT_EQ(1, network_.send_query_call_count);
+
+  // After load, another surface doesn't trigger any tasks.
+  TestSurface later_surface;
+  stream_->AttachSurface(&later_surface);
+
+  EXPECT_TRUE(IsTaskQueueIdle());
+}
+
+TEST_F(FeedStreamTest, ModelChangesAreSavedToStorage) {
+  store_->SaveFullStream(MakeTypicalInitialModelState(), base::DoNothing());
+  TestSurface surface;
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+  ASSERT_TRUE(surface.initial_state);
+
+  // Remove #1, add #2.
+  const std::vector<feedstore::DataOperation> operations = {
+      MakeOperation(MakeRemove(MakeClusterId(1))),
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  };
+  stream_->ExecuteOperations(operations);
+
+  WaitForIdleTaskQueue();
+
+  // Verify changes are applied to storage.
+  EXPECT_STRINGS_EQUAL(
+      ModelStateFor(MakeTypicalInitialModelState(), operations),
+      ModelStateFor(store_.get()));
+
+  // Unload and reload the model from the store, and verify we can still apply
+  // operations correctly.
+  stream_->DetachSurface(&surface);
+  surface.Clear();
+  UnloadModel();
+  stream_->AttachSurface(&surface);
+  WaitForIdleTaskQueue();
+  ASSERT_TRUE(surface.initial_state);
+
+  // Remove #2, add #3.
+  const std::vector<feedstore::DataOperation> operations2 = {
+      MakeOperation(MakeRemove(MakeClusterId(2))),
+      MakeOperation(MakeCluster(3, MakeRootId())),
+      MakeOperation(MakeContentNode(3, MakeClusterId(3))),
+      MakeOperation(MakeContent(3)),
+  };
+  stream_->ExecuteOperations(operations2);
+
+  WaitForIdleTaskQueue();
+  EXPECT_STRINGS_EQUAL(
+      ModelStateFor(MakeTypicalInitialModelState(), operations, operations2),
+      ModelStateFor(store_.get()));
+}
+
+}  // namespace
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/prefs.cc b/chromium/components/feed/core/v2/prefs.cc
new file mode 100644
index 00000000000..d3d5a0b39f2
--- /dev/null
+++ b/chromium/components/feed/core/v2/prefs.cc
@@ -0,0 +1,56 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/prefs.h"
+
+#include <utility>
+
+#include "base/value_conversions.h"
+#include "base/values.h"
+#include "components/prefs/pref_registry_simple.h"
+#include "components/prefs/pref_service.h"
+
+namespace feed {
+namespace {
+const char kThrottlerRequestCountListPrefName[] =
+    "feedv2.request_throttler.request_counts";
+const char kThrottlerLastRequestTime[] =
+    "feedv2.request_throttler.last_request_time";
+
+}  // namespace
+
+namespace prefs {
+
+std::vector<int> GetThrottlerRequestCounts(PrefService* pref_service) {
+  std::vector<int> result;
+  const auto& value_list =
+      pref_service->GetList(kThrottlerRequestCountListPrefName)->GetList();
+  for (const base::Value& value : value_list) {
+    result.push_back(value.is_int() ? value.GetInt() : 0);
+  }
+  return result;
+}
+
+void SetThrottlerRequestCounts(std::vector<int> request_counts,
+                               PrefService* pref_service) {
+  std::vector<base::Value> value_list;
+  for (int count : request_counts) {
+    value_list.push_back(base::Value(count));
+  }
+
+  pref_service->Set(kThrottlerRequestCountListPrefName,
+                    base::Value(std::move(value_list)));
+}
+
+base::Time GetLastRequestTime(PrefService* pref_service) {
+  return pref_service->GetTime(kThrottlerLastRequestTime);
+}
+
+void SetLastRequestTime(base::Time request_time, PrefService* pref_service) {
+  return pref_service->SetTime(kThrottlerLastRequestTime, request_time);
+}
+
+}  // namespace prefs
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/prefs.h b/chromium/components/feed/core/v2/prefs.h
new file mode 100644
index 00000000000..29da3c9c6cf
--- /dev/null
+++ b/chromium/components/feed/core/v2/prefs.h
@@ -0,0 +1,33 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_PREFS_H_
+#define COMPONENTS_FEED_CORE_V2_PREFS_H_
+
+#include <vector>
+
+#include "base/time/time.h"
+
+class PrefService;
+
+namespace feed {
+namespace prefs {
+
+// Functions for accessing prefs.
+
+// For counting previously made requests, one integer for each
+// |NetworkRequestType|.
+std::vector<int> GetThrottlerRequestCounts(PrefService* pref_service);
+void SetThrottlerRequestCounts(std::vector<int> request_counts,
+                               PrefService* pref_service);
+
+// Time of the last request. For determining whether the next day's quota should
+// be released.
+base::Time GetLastRequestTime(PrefService* pref_service);
+void SetLastRequestTime(base::Time request_time, PrefService* pref_service);
+
+}  // namespace prefs
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_PREFS_H_
diff --git a/chromium/components/feed/core/v2/proto_util.cc b/chromium/components/feed/core/v2/proto_util.cc
new file mode 100644
index 00000000000..90029710307
--- /dev/null
+++ b/chromium/components/feed/core/v2/proto_util.cc
@@ -0,0 +1,49 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/proto_util.h"
+
+#include <tuple>
+
+#include "base/strings/strcat.h"
+#include "base/strings/string_number_conversions.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+
+namespace feed {
+
+std::string ContentIdString(const feedwire::ContentId& content_id) {
+  return base::StrCat({content_id.content_domain(), ",",
+                       base::NumberToString(content_id.type()), ",",
+                       base::NumberToString(content_id.id())});
+}
+
+bool Equal(const feedwire::ContentId& a, const feedwire::ContentId& b) {
+  return a.content_domain() == b.content_domain() && a.id() == b.id() &&
+         a.type() == b.type();
+}
+
+bool CompareContentId(const feedwire::ContentId& a,
+                      const feedwire::ContentId& b) {
+  // Local variables because tie() needs l-values.
+  const int a_id = a.id();
+  const int b_id = b.id();
+  const feedwire::ContentId::Type a_type = a.type();
+  const feedwire::ContentId::Type b_type = b.type();
+  return std::tie(a.content_domain(), a_id, a_type) <
+         std::tie(b.content_domain(), b_id, b_type);
+}
+
+}  // namespace feed
+
+namespace feedstore {
+void SetLastAddedTime(base::Time t, feedstore::StreamData* data) {
+  data->set_last_added_time_millis(
+      (t - base::Time::UnixEpoch()).InMilliseconds());
+}
+
+base::Time GetLastAddedTime(const feedstore::StreamData& data) {
+  return base::Time::UnixEpoch() +
+         base::TimeDelta::FromMilliseconds(data.last_added_time_millis());
+}
+}  // namespace feedstore
diff --git a/chromium/components/feed/core/v2/proto_util.h b/chromium/components/feed/core/v2/proto_util.h
new file mode 100644
index 00000000000..c7700625eb7
--- /dev/null
+++ b/chromium/components/feed/core/v2/proto_util.h
@@ -0,0 +1,44 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_PROTO_UTIL_H_
+#define COMPONENTS_FEED_CORE_V2_PROTO_UTIL_H_
+
+#include <string>
+
+#include "base/time/time.h"
+
+#include "components/feed/core/proto/v2/wire/content_id.pb.h"
+
+namespace feedstore {
+class StreamData;
+}
+
+// Helper functions/classes for dealing with feed proto messages.
+
+namespace feed {
+
+std::string ContentIdString(const feedwire::ContentId&);
+bool Equal(const feedwire::ContentId& a, const feedwire::ContentId& b);
+bool CompareContentId(const feedwire::ContentId& a,
+                      const feedwire::ContentId& b);
+
+class ContentIdCompareFunctor {
+ public:
+  bool operator()(const feedwire::ContentId& a,
+                  const feedwire::ContentId& b) const {
+    return CompareContentId(a, b);
+  }
+};
+
+}  // namespace feed
+
+namespace feedstore {
+
+void SetLastAddedTime(base::Time t, feedstore::StreamData* data);
+base::Time GetLastAddedTime(const feedstore::StreamData& data);
+
+}  // namespace feedstore
+
+#endif  // COMPONENTS_FEED_CORE_V2_PROTO_UTIL_H_
diff --git a/chromium/components/feed/core/v2/public/feed_service.cc b/chromium/components/feed/core/v2/public/feed_service.cc
new file mode 100644
index 00000000000..d1fb36f1fd9
--- /dev/null
+++ b/chromium/components/feed/core/v2/public/feed_service.cc
@@ -0,0 +1,113 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/public/feed_service.h"
+
+#include <utility>
+
+#include "base/time/default_clock.h"
+#include "base/time/default_tick_clock.h"
+#include "components/feed/core/v2/feed_network_impl.h"
+#include "components/feed/core/v2/feed_store.h"
+#include "components/feed/core/v2/feed_stream.h"
+#include "components/feed/core/v2/refresh_task_scheduler.h"
+#include "net/base/network_change_notifier.h"
+#include "services/network/public/cpp/shared_url_loader_factory.h"
+
+namespace feed {
+namespace {
+
+class EulaObserver : public web_resource::EulaAcceptedNotifier::Observer {
+ public:
+  explicit EulaObserver(FeedStream* feed_stream) : feed_stream_(feed_stream) {}
+  EulaObserver(EulaObserver&) = delete;
+  EulaObserver& operator=(const EulaObserver&) = delete;
+
+  // web_resource::EulaAcceptedNotifier::Observer.
+  void OnEulaAccepted() override { feed_stream_->OnEulaAccepted(); }
+
+ private:
+  FeedStream* feed_stream_;
+};
+
+}  // namespace
+
+class FeedService::NetworkDelegateImpl : public FeedNetworkImpl::Delegate {
+ public:
+  explicit NetworkDelegateImpl(FeedService::Delegate* service_delegate)
+      : service_delegate_(service_delegate) {}
+  NetworkDelegateImpl(const NetworkDelegateImpl&) = delete;
+  NetworkDelegateImpl& operator=(const NetworkDelegateImpl&) = delete;
+
+  // FeedNetworkImpl::Delegate.
+  std::string GetLanguageTag() override {
+    return service_delegate_->GetLanguageTag();
+  }
+
+ private:
+  FeedService::Delegate* service_delegate_;
+};
+
+class FeedService::StreamDelegateImpl : public FeedStream::Delegate {
+ public:
+  explicit StreamDelegateImpl(PrefService* local_state)
+      : eula_notifier_(local_state) {}
+  StreamDelegateImpl(const StreamDelegateImpl&) = delete;
+  StreamDelegateImpl& operator=(const StreamDelegateImpl&) = delete;
+
+  void Initialize(FeedStream* feed_stream) {
+    eula_observer_ = std::make_unique<EulaObserver>(feed_stream);
+    eula_notifier_.Init(eula_observer_.get());
+  }
+
+  // FeedStream::Delegate.
+  bool IsEulaAccepted() override { return eula_notifier_.IsEulaAccepted(); }
+  bool IsOffline() override { return net::NetworkChangeNotifier::IsOffline(); }
+
+ private:
+  web_resource::EulaAcceptedNotifier eula_notifier_;
+  std::unique_ptr<EulaObserver> eula_observer_;
+};
+
+FeedService::FeedService(std::unique_ptr<FeedStreamApi> stream)
+    : stream_(std::move(stream)) {}
+
+FeedService::FeedService(
+    std::unique_ptr<Delegate> delegate,
+    std::unique_ptr<RefreshTaskScheduler> refresh_task_scheduler,
+    PrefService* profile_prefs,
+    PrefService* local_state,
+    std::unique_ptr<leveldb_proto::ProtoDatabase<feedstore::Record>> database,
+    signin::IdentityManager* identity_manager,
+    scoped_refptr<network::SharedURLLoaderFactory> url_loader_factory,
+    scoped_refptr<base::SequencedTaskRunner> background_task_runner,
+    const std::string& api_key)
+    : delegate_(std::move(delegate)),
+      refresh_task_scheduler_(std::move(refresh_task_scheduler)) {
+  stream_delegate_ = std::make_unique<StreamDelegateImpl>(local_state);
+  network_delegate_ = std::make_unique<NetworkDelegateImpl>(delegate_.get());
+  feed_network_ = std::make_unique<FeedNetworkImpl>(
+      network_delegate_.get(), identity_manager, api_key, url_loader_factory,
+      base::DefaultTickClock::GetInstance(), profile_prefs);
+  store_ = std::make_unique<FeedStore>(std::move(database));
+
+  stream_ = std::make_unique<FeedStream>(
+      refresh_task_scheduler_.get(),
+      nullptr,  // TODO(harringtond): Implement EventObserver.
+      stream_delegate_.get(), profile_prefs, feed_network_.get(), store_.get(),
+      base::DefaultClock::GetInstance(), base::DefaultTickClock::GetInstance(),
+      background_task_runner);
+
+  stream_delegate_->Initialize(static_cast<FeedStream*>(stream_.get()));
+
+  // TODO(harringtond): Call FeedStream::OnSignedIn()
+  // TODO(harringtond): Call FeedStream::OnSignedOut()
+  // TODO(harringtond): Call FeedStream::OnHistoryDeleted()
+  // TODO(harringtond): Call FeedStream::OnCacheDataCleared()
+  // TODO(harringtond): Call FeedStream::OnEnterForeground()
+}
+
+FeedService::~FeedService() = default;
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/public/feed_service.h b/chromium/components/feed/core/v2/public/feed_service.h
new file mode 100644
index 00000000000..2d24ad0d0f6
--- /dev/null
+++ b/chromium/components/feed/core/v2/public/feed_service.h
@@ -0,0 +1,85 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_PUBLIC_FEED_SERVICE_H_
+#define COMPONENTS_FEED_CORE_V2_PUBLIC_FEED_SERVICE_H_
+
+#include <memory>
+#include <string>
+
+#include "base/files/file_path.h"
+#include "base/memory/scoped_refptr.h"
+#include "components/feed/core/v2/public/feed_stream_api.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "components/leveldb_proto/public/proto_database.h"
+#include "components/web_resource/eula_accepted_notifier.h"
+
+namespace base {
+class SequencedTaskRunner;
+}
+namespace feedstore {
+class Record;
+}
+namespace network {
+class SharedURLLoaderFactory;
+}
+namespace signin {
+class IdentityManager;
+}
+
+namespace feed {
+class RefreshTaskScheduler;
+class FeedNetwork;
+class FeedStore;
+
+class FeedService : public KeyedService {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() = default;
+    // Returns a string which represents the top locale and region of the
+    // device.
+    virtual std::string GetLanguageTag() = 0;
+  };
+
+  // Construct a FeedService given an already constructed FeedStreamApi.
+  // Used for testing only.
+  explicit FeedService(std::unique_ptr<FeedStreamApi> stream);
+
+  // Construct a new FeedStreamApi along with FeedService.
+  FeedService(
+      std::unique_ptr<Delegate> delegate,
+      std::unique_ptr<RefreshTaskScheduler> refresh_task_scheduler,
+      PrefService* profile_prefs,
+      PrefService* local_state,
+      std::unique_ptr<leveldb_proto::ProtoDatabase<feedstore::Record>> database,
+      signin::IdentityManager* identity_manager,
+      scoped_refptr<network::SharedURLLoaderFactory> url_loader_factory,
+      scoped_refptr<base::SequencedTaskRunner> background_task_runner,
+      const std::string& api_key);
+  ~FeedService() override;
+  FeedService(const FeedService&) = delete;
+  FeedService& operator=(const FeedService&) = delete;
+
+  FeedStreamApi* GetStream() { return stream_.get(); }
+
+ private:
+  class StreamDelegateImpl;
+  class NetworkDelegateImpl;
+
+  // These components are owned for construction of |FeedStreamApi|. These will
+  // be null if |FeedStreamApi| is created externally.
+  std::unique_ptr<Delegate> delegate_;
+  std::unique_ptr<StreamDelegateImpl> stream_delegate_;
+  std::unique_ptr<NetworkDelegateImpl> network_delegate_;
+  std::unique_ptr<FeedNetwork> feed_network_;
+  std::unique_ptr<FeedStore> store_;
+  std::unique_ptr<RefreshTaskScheduler> refresh_task_scheduler_;
+
+  std::unique_ptr<FeedStreamApi> stream_;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_PUBLIC_FEED_SERVICE_H_
diff --git a/chromium/components/feed/core/v2/public/feed_stream_api.h b/chromium/components/feed/core/v2/public/feed_stream_api.h
new file mode 100644
index 00000000000..46a025c71fe
--- /dev/null
+++ b/chromium/components/feed/core/v2/public/feed_stream_api.h
@@ -0,0 +1,66 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_PUBLIC_FEED_STREAM_API_H_
+#define COMPONENTS_FEED_CORE_V2_PUBLIC_FEED_STREAM_API_H_
+
+#include <vector>
+
+#include "base/observer_list_types.h"
+#include "base/util/type_safety/id_type.h"
+#include "components/feed/core/proto/v2/wire/content_id.pb.h"
+
+namespace feedui {
+class StreamUpdate;
+}
+namespace feedstore {
+class DataOperation;
+}
+
+namespace feed {
+using ContentId = feedwire::ContentId;
+// Uniquely identifies a revision of a |feedstore::Content|. If Content changes,
+// it is assigned a new revision number.
+using ContentRevision = util::IdTypeU32<class ContentRevisionClass>;
+// A unique ID for an ephemeral change.
+using EphemeralChangeId = util::IdTypeU32<class EphemeralChangeIdClass>;
+
+// This is the public access point for interacting with the Feed stream
+// contents.
+class FeedStreamApi {
+ public:
+  class SurfaceInterface : public base::CheckedObserver {
+   public:
+    // Called after registering the observer to provide the full stream state.
+    // Also called whenever the stream changes.
+    virtual void StreamUpdate(const feedui::StreamUpdate&) = 0;
+  };
+
+  FeedStreamApi() = default;
+  virtual ~FeedStreamApi() = default;
+
+  virtual void AttachSurface(SurfaceInterface*) = 0;
+  virtual void DetachSurface(SurfaceInterface*) = 0;
+
+  virtual void SetArticlesListVisible(bool is_visible) = 0;
+  virtual bool IsArticlesListVisible() = 0;
+
+  // Apply |operations| to the stream model. Does nothing if the model is not
+  // yet loaded.
+  virtual void ExecuteOperations(
+      std::vector<feedstore::DataOperation> operations) = 0;
+
+  // Create a temporary change that may be undone or committed later. Does
+  // nothing if the model is not yet loaded.
+  virtual EphemeralChangeId CreateEphemeralChange(
+      std::vector<feedstore::DataOperation> operations) = 0;
+  // Commits a change. Returns false if the change does not exist.
+  virtual bool CommitEphemeralChange(EphemeralChangeId id) = 0;
+  // Rejects a change. Returns false if the change does not exist.
+  virtual bool RejectEphemeralChange(EphemeralChangeId id) = 0;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_PUBLIC_FEED_STREAM_API_H_
diff --git a/chromium/components/feed/core/v2/refresh_task_scheduler.h b/chromium/components/feed/core/v2/refresh_task_scheduler.h
new file mode 100644
index 00000000000..6f27dd57161
--- /dev/null
+++ b/chromium/components/feed/core/v2/refresh_task_scheduler.h
@@ -0,0 +1,32 @@
+
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_REFRESH_TASK_SCHEDULER_H_
+#define COMPONENTS_FEED_CORE_V2_REFRESH_TASK_SCHEDULER_H_
+
+#include "base/time/time.h"
+
+namespace feed {
+
+// Schedules a repeating background task for refreshing the Feed.
+// When the scheduled task executes, it calls FeedStream::ExecuteRefreshTask().
+class RefreshTaskScheduler {
+ public:
+  RefreshTaskScheduler() = default;
+  virtual ~RefreshTaskScheduler() = default;
+
+  // Schedules the task if it is not yet scheduled, or if the scheduling
+  // period changes.
+  virtual void EnsureScheduled(base::TimeDelta period) = 0;
+  // Cancel the task if it was previously scheduled.
+  virtual void Cancel() = 0;
+  // After FeedStream::ExecuteRefreshTask is called, the callee must call this
+  // function to indicate the work is complete.
+  virtual void RefreshTaskComplete() = 0;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_REFRESH_TASK_SCHEDULER_H_
diff --git a/chromium/components/feed/core/v2/request_throttler.cc b/chromium/components/feed/core/v2/request_throttler.cc
new file mode 100644
index 00000000000..95d4d8b5edd
--- /dev/null
+++ b/chromium/components/feed/core/v2/request_throttler.cc
@@ -0,0 +1,76 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/request_throttler.h"
+
+#include <vector>
+
+#include "base/time/clock.h"
+#include "components/feed/core/v2/prefs.h"
+#include "components/prefs/pref_service.h"
+
+namespace feed {
+namespace {
+int GetMaxRequestsPerDay(NetworkRequestType request_type) {
+  // TODO(harringtond): Decide what launchable values are.
+  switch (request_type) {
+    case NetworkRequestType::kFeedQuery:
+      return 20;
+    case NetworkRequestType::kUploadActions:
+      return 20;
+  }
+}
+
+int DaysSinceOrigin(const base::Time& time_value) {
+  // |LocalMidnight()| DCHECKs on some platforms if |time_value| is too small
+  // (like zero). So if time is before the unix epoch, return 0.
+  return time_value < base::Time::UnixEpoch()
+             ? 0
+             : time_value.LocalMidnight().since_origin().InDays();
+}
+
+}  // namespace
+
+RequestThrottler::RequestThrottler(PrefService* pref_service,
+                                   const base::Clock* clock)
+    : pref_service_(pref_service), clock_(clock) {
+  DCHECK(pref_service);
+  DCHECK(clock);
+}
+
+bool RequestThrottler::RequestQuota(NetworkRequestType request_type) {
+  ResetCountersIfDayChanged();
+
+  const int max_requests_per_day = GetMaxRequestsPerDay(request_type);
+
+  // Fetch request counts from prefs. There's an entry for each request type.
+  // We may need to resize the list.
+  std::vector<int> request_counts =
+      feed::prefs::GetThrottlerRequestCounts(pref_service_);
+  const size_t request_count_index = static_cast<size_t>(request_type);
+  if (request_counts.size() <= request_count_index)
+    request_counts.resize(request_count_index + 1);
+
+  int& requests_already_made = request_counts[request_count_index];
+  if (requests_already_made >= max_requests_per_day)
+    return false;
+  requests_already_made++;
+  feed::prefs::SetThrottlerRequestCounts(request_counts, pref_service_);
+  return true;
+}
+
+void RequestThrottler::ResetCountersIfDayChanged() {
+  // Grant new quota on local midnight to spread out when clients that start
+  // making un-throttled requests to server.
+  const base::Time now = clock_->Now();
+  const bool day_changed =
+      DaysSinceOrigin(feed::prefs::GetLastRequestTime(pref_service_)) !=
+      DaysSinceOrigin(now);
+  feed::prefs::SetLastRequestTime(now, pref_service_);
+
+  if (day_changed)
+    feed::prefs::SetThrottlerRequestCounts({}, pref_service_);
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/request_throttler.h b/chromium/components/feed/core/v2/request_throttler.h
new file mode 100644
index 00000000000..344d600f24f
--- /dev/null
+++ b/chromium/components/feed/core/v2/request_throttler.h
@@ -0,0 +1,41 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_REQUEST_THROTTLER_H_
+#define COMPONENTS_FEED_CORE_V2_REQUEST_THROTTLER_H_
+
+#include "components/feed/core/v2/enums.h"
+
+class PrefService;
+namespace base {
+class Clock;
+}
+
+namespace feed {
+
+// Limits number of network requests that can be made each day.
+class RequestThrottler {
+ public:
+  RequestThrottler(PrefService* pref_service, const base::Clock* clock);
+
+  RequestThrottler(const RequestThrottler&) = delete;
+  RequestThrottler& operator=(const RequestThrottler&) = delete;
+
+  // Returns whether quota is available for another request, persists the usage
+  // of said quota, and reports this information to UMA.
+  bool RequestQuota(NetworkRequestType request_type);
+
+ private:
+  void ResetCountersIfDayChanged();
+
+  // Provides durable storage.
+  PrefService* pref_service_;
+
+  // Used to access current time, injected for testing.
+  const base::Clock* clock_;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_REQUEST_THROTTLER_H_
diff --git a/chromium/components/feed/core/v2/request_throttler_unittest.cc b/chromium/components/feed/core/v2/request_throttler_unittest.cc
new file mode 100644
index 00000000000..0cf0e98f3b0
--- /dev/null
+++ b/chromium/components/feed/core/v2/request_throttler_unittest.cc
@@ -0,0 +1,55 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/request_throttler.h"
+
+#include <memory>
+
+#include "base/test/simple_test_clock.h"
+#include "components/feed/core/common/pref_names.h"
+#include "components/prefs/testing_pref_service.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace feed {
+namespace {
+
+const int kMaximumQueryRequestsPerDay = 20;
+
+class FeedRequestThrottlerTest : public testing::Test {
+ public:
+  FeedRequestThrottlerTest() {
+    RegisterProfilePrefs(test_prefs_.registry());
+
+    base::Time now;
+    EXPECT_TRUE(base::Time::FromString("2018-06-11 12:01AM", &now));
+    test_clock_.SetNow(now);
+  }
+
+ protected:
+  TestingPrefServiceSimple test_prefs_;
+  base::SimpleTestClock test_clock_;
+  RequestThrottler throttler_{&test_prefs_, &test_clock_};
+};
+
+TEST_F(FeedRequestThrottlerTest, RequestQuotaAllAtOnce) {
+  for (int i = 0; i < kMaximumQueryRequestsPerDay; ++i) {
+    EXPECT_TRUE(throttler_.RequestQuota(NetworkRequestType::kFeedQuery));
+  }
+  EXPECT_FALSE(throttler_.RequestQuota(NetworkRequestType::kFeedQuery));
+}
+
+TEST_F(FeedRequestThrottlerTest, QuotaIsPerDay) {
+  for (int i = 0; i < kMaximumQueryRequestsPerDay; ++i) {
+    EXPECT_TRUE(throttler_.RequestQuota(NetworkRequestType::kUploadActions));
+  }
+  // Because we started at 12:01AM, we need to advance 24 hours before making
+  // another successful request.
+  test_clock_.Advance(base::TimeDelta::FromHours(23));
+  EXPECT_FALSE(throttler_.RequestQuota(NetworkRequestType::kUploadActions));
+  test_clock_.Advance(base::TimeDelta::FromHours(1));
+  EXPECT_TRUE(throttler_.RequestQuota(NetworkRequestType::kUploadActions));
+}
+
+}  // namespace
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/scheduling.cc b/chromium/components/feed/core/v2/scheduling.cc
new file mode 100644
index 00000000000..21511470cf2
--- /dev/null
+++ b/chromium/components/feed/core/v2/scheduling.cc
@@ -0,0 +1,51 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/scheduling.h"
+#include "base/time/time.h"
+
+namespace feed {
+
+base::TimeDelta GetUserClassTriggerThreshold(UserClass user_class,
+                                             TriggerType trigger) {
+  switch (user_class) {
+    case UserClass::kRareSuggestionsViewer:
+      switch (trigger) {
+        case TriggerType::kNtpShown:
+          return base::TimeDelta::FromHours(4);
+        case TriggerType::kForegrounded:
+          return base::TimeDelta::FromHours(24);
+        case TriggerType::kFixedTimer:
+          return base::TimeDelta::FromHours(96);
+      }
+    case UserClass::kActiveSuggestionsViewer:
+      switch (trigger) {
+        case TriggerType::kNtpShown:
+          return base::TimeDelta::FromHours(4);
+        case TriggerType::kForegrounded:
+          return base::TimeDelta::FromHours(24);
+        case TriggerType::kFixedTimer:
+          return base::TimeDelta::FromHours(48);
+      }
+    case UserClass::kActiveSuggestionsConsumer:
+      switch (trigger) {
+        case TriggerType::kNtpShown:
+          return base::TimeDelta::FromHours(1);
+        case TriggerType::kForegrounded:
+          return base::TimeDelta::FromHours(12);
+        case TriggerType::kFixedTimer:
+          return base::TimeDelta::FromHours(24);
+      }
+  }
+}
+
+bool ShouldWaitForNewContent(UserClass user_class,
+                             bool has_content,
+                             base::TimeDelta content_age) {
+  return !has_content ||
+         content_age > GetUserClassTriggerThreshold(user_class,
+                                                    TriggerType::kForegrounded);
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/scheduling.h b/chromium/components/feed/core/v2/scheduling.h
new file mode 100644
index 00000000000..3361fc66c74
--- /dev/null
+++ b/chromium/components/feed/core/v2/scheduling.h
@@ -0,0 +1,30 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_SCHEDULING_H_
+#define COMPONENTS_FEED_CORE_V2_SCHEDULING_H_
+
+#include "base/time/time.h"
+#include "components/feed/core/v2/enums.h"
+
+namespace feed {
+constexpr base::TimeDelta kSuppressRefreshDuration =
+    base::TimeDelta::FromMinutes(30);
+
+// Returns a duration, T, depending on the UserClass and TriggerType.
+// The following should be true:
+// - At most one fetch is attempted per T.
+// - Content is considered stale if time since last fetch is > T. We'll prefer
+//   to refresh stale content before showing it.
+// - For TriggerType::kFixedTimer, T is the time between scheduled fetches.
+base::TimeDelta GetUserClassTriggerThreshold(UserClass user_class,
+                                             TriggerType trigger);
+
+// Returns whether we should wait for new content before showing stream content.
+bool ShouldWaitForNewContent(UserClass user_class,
+                             bool has_content,
+                             base::TimeDelta content_age);
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_SCHEDULING_H_
diff --git a/chromium/components/feed/core/v2/stream_event_metrics.cc b/chromium/components/feed/core/v2/stream_event_metrics.cc
new file mode 100644
index 00000000000..ffce8fa1198
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_event_metrics.cc
@@ -0,0 +1,28 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+#include "components/feed/core/v2/stream_event_metrics.h"
+
+#include "base/metrics/histogram_macros.h"
+
+namespace feed {
+
+void StreamEventMetrics::OnLoadStream(LoadStreamStatus load_from_store_status,
+                                      LoadStreamStatus final_status) {
+  // TODO(harringtond): Add UMA for this, or record it with another histogram.
+}
+
+void StreamEventMetrics::OnMaybeTriggerRefresh(TriggerType trigger,
+                                               bool clear_all_before_refresh) {
+  // TODO(harringtond): Either add UMA for this or remove it.
+}
+
+void StreamEventMetrics::OnClearAll(base::TimeDelta time_since_last_clear) {
+  UMA_HISTOGRAM_CUSTOM_TIMES(
+      "ContentSuggestions.Feed.Scheduler.TimeSinceLastFetchOnClear",
+      time_since_last_clear, base::TimeDelta::FromSeconds(1),
+      base::TimeDelta::FromDays(7),
+      /*bucket_count=*/50);
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/stream_event_metrics.h b/chromium/components/feed/core/v2/stream_event_metrics.h
new file mode 100644
index 00000000000..3940c2f428c
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_event_metrics.h
@@ -0,0 +1,24 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_STREAM_EVENT_METRICS_H_
+#define COMPONENTS_FEED_CORE_V2_STREAM_EVENT_METRICS_H_
+
+#include "components/feed/core/v2/enums.h"
+#include "components/feed/core/v2/feed_stream.h"
+
+namespace feed {
+
+// Reports UMA metrics for stream events.
+class StreamEventMetrics : public FeedStream::EventObserver {
+ public:
+  void OnLoadStream(LoadStreamStatus load_from_store_status,
+                    LoadStreamStatus final_status) override;
+  void OnMaybeTriggerRefresh(TriggerType trigger,
+                             bool clear_all_before_refresh) override;
+  void OnClearAll(base::TimeDelta time_since_last_clear) override;
+};
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_STREAM_EVENT_METRICS_H_
diff --git a/chromium/components/feed/core/v2/stream_model.cc b/chromium/components/feed/core/v2/stream_model.cc
new file mode 100644
index 00000000000..74381e4516e
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model.cc
@@ -0,0 +1,229 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/stream_model.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "base/logging.h"
+#include "base/strings/strcat.h"
+#include "base/strings/string_number_conversions.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/proto/v2/wire/content_id.pb.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+
+namespace feed {
+namespace {
+bool HasClearAll(const std::vector<feedstore::StreamStructure>& structures) {
+  for (const feedstore::StreamStructure& data : structures) {
+    if (data.operation() == feedstore::StreamStructure::CLEAR_ALL)
+      return true;
+  }
+  return false;
+}
+}  // namespace
+StreamModel::UiUpdate::UiUpdate() = default;
+StreamModel::UiUpdate::~UiUpdate() = default;
+StreamModel::UiUpdate::UiUpdate(const UiUpdate&) = default;
+StreamModel::UiUpdate& StreamModel::UiUpdate::operator=(const UiUpdate&) =
+    default;
+StreamModel::StoreUpdate::StoreUpdate() = default;
+StreamModel::StoreUpdate::~StoreUpdate() = default;
+StreamModel::StoreUpdate::StoreUpdate(const StoreUpdate&) = default;
+StreamModel::StoreUpdate& StreamModel::StoreUpdate::operator=(
+    const StoreUpdate&) = default;
+StreamModel::StoreUpdate::StoreUpdate(StoreUpdate&&) = default;
+StreamModel::StoreUpdate& StreamModel::StoreUpdate::operator=(StoreUpdate&&) =
+    default;
+
+StreamModel::StreamModel() = default;
+StreamModel::~StreamModel() = default;
+
+void StreamModel::SetStoreObserver(StoreObserver* store_observer) {
+  DCHECK(!store_observer || !store_observer_)
+      << "Attempting to set store_observer multiple times";
+  store_observer_ = store_observer;
+}
+
+void StreamModel::SetObserver(Observer* observer) {
+  DCHECK(!observer || !observer_)
+      << "Attempting to set the observer multiple times";
+  observer_ = observer;
+}
+
+const feedstore::Content* StreamModel::FindContent(
+    ContentRevision revision) const {
+  return GetFinalFeatureTree()->FindContent(revision);
+}
+const std::string* StreamModel::FindSharedStateData(
+    const std::string& id) const {
+  auto iter = shared_states_.find(id);
+  if (iter != shared_states_.end()) {
+    return &iter->second.data;
+  }
+  return nullptr;
+}
+
+std::vector<std::string> StreamModel::GetSharedStateIds() const {
+  std::vector<std::string> ids;
+  for (auto& entry : shared_states_) {
+    ids.push_back(entry.first);
+  }
+  return ids;
+}
+
+void StreamModel::Update(
+    std::unique_ptr<StreamModelUpdateRequest> update_request) {
+  feedstore::StreamData& stream_data = update_request->stream_data;
+  std::vector<feedstore::StreamStructure>& stream_structures =
+      update_request->stream_structures;
+  if (HasClearAll(stream_structures)) {
+    shared_states_.clear();
+  }
+
+  // Update the feature tree.
+  for (const feedstore::StreamStructure& structure : stream_structures) {
+    base_feature_tree_.ApplyStreamStructure(structure);
+  }
+  for (feedstore::Content& content : update_request->content) {
+    base_feature_tree_.AddContent(std::move(content));
+  }
+
+  // Update non-tree data.
+  next_page_token_ = stream_data.next_page_token();
+  last_added_time_ =
+      base::Time::UnixEpoch() +
+      base::TimeDelta::FromMilliseconds(stream_data.last_added_time_millis());
+  consistency_token_ = stream_data.consistency_token();
+
+  for (feedstore::StreamSharedState& shared_state :
+       update_request->shared_states) {
+    std::string id = ContentIdString(shared_state.content_id());
+    if (!shared_states_.contains(id)) {
+      shared_states_[id].data =
+          std::move(*shared_state.mutable_shared_state_data());
+    }
+  }
+
+  // Set next_structure_sequence_number_ when doing the initial load.
+  if (update_request->source ==
+      StreamModelUpdateRequest::Source::kInitialLoadFromStore) {
+    next_structure_sequence_number_ =
+        update_request->max_structure_sequence_number + 1;
+  }
+
+  // TODO(harringtond): Some StreamData fields not yet used.
+  //    next_action_id - do we need to load the model before uploading
+  //         actions? If not, we probably will want to move this out of
+  //         StreamData.
+  //    content_id - probably just ignore for now
+
+  UpdateFlattenedTree();
+}
+
+EphemeralChangeId StreamModel::CreateEphemeralChange(
+    std::vector<feedstore::DataOperation> operations) {
+  const EphemeralChangeId id =
+      ephemeral_changes_.AddEphemeralChange(std::move(operations))->id();
+
+  UpdateFlattenedTree();
+
+  return id;
+}
+
+void StreamModel::ExecuteOperations(
+    std::vector<feedstore::DataOperation> operations) {
+  for (const feedstore::DataOperation& operation : operations) {
+    if (operation.has_structure()) {
+      base_feature_tree_.ApplyStreamStructure(operation.structure());
+    }
+    if (operation.has_content()) {
+      base_feature_tree_.AddContent(operation.content());
+    }
+  }
+
+  if (store_observer_) {
+    StoreUpdate store_update;
+    store_update.operations = std::move(operations);
+    store_update.sequence_number = next_structure_sequence_number_++;
+    store_observer_->OnStoreChange(std::move(store_update));
+  }
+
+  UpdateFlattenedTree();
+}
+
+bool StreamModel::CommitEphemeralChange(EphemeralChangeId id) {
+  std::unique_ptr<stream_model::EphemeralChange> change =
+      ephemeral_changes_.Remove(id);
+  if (!change)
+    return false;
+
+  // Note: it's possible that the does change even upon commit because it
+  // may change the order that operations are applied. ExecuteOperations
+  // will ensure observers are updated.
+  ExecuteOperations(change->GetOperations());
+  return true;
+}
+
+bool StreamModel::RejectEphemeralChange(EphemeralChangeId id) {
+  if (ephemeral_changes_.Remove(id)) {
+    UpdateFlattenedTree();
+    return true;
+  }
+  return false;
+}
+
+void StreamModel::UpdateFlattenedTree() {
+  if (ephemeral_changes_.GetChangeList().empty()) {
+    feature_tree_after_changes_.reset();
+  } else {
+    feature_tree_after_changes_ =
+        ApplyEphemeralChanges(base_feature_tree_, ephemeral_changes_);
+  }
+  // Update list of visible content.
+  std::vector<ContentRevision> new_state =
+      GetFinalFeatureTree()->GetVisibleContent();
+  const bool content_list_changed = content_list_ != new_state;
+  content_list_ = std::move(new_state);
+
+  // Pack and send UiUpdate.
+  UiUpdate update;
+  update.content_list_changed = content_list_changed;
+  for (auto& entry : shared_states_) {
+    SharedState& shared_state = entry.second;
+    UiUpdate::SharedStateInfo info;
+    info.shared_state_id = entry.first;
+    info.updated = shared_state.updated;
+    update.shared_states.push_back(std::move(info));
+
+    shared_state.updated = false;
+  }
+
+  if (observer_)
+    observer_->OnUiUpdate(update);
+}
+
+stream_model::FeatureTree* StreamModel::GetFinalFeatureTree() {
+  return feature_tree_after_changes_ ? feature_tree_after_changes_.get()
+                                     : &base_feature_tree_;
+}
+const stream_model::FeatureTree* StreamModel::GetFinalFeatureTree() const {
+  return const_cast<StreamModel*>(this)->GetFinalFeatureTree();
+}
+
+std::string StreamModel::DumpStateForTesting() {
+  std::stringstream ss;
+  ss << "StreamModel{\n";
+  ss << "next_page_token='" << next_page_token_ << "'\n";
+  ss << "consistency_token='" << consistency_token_ << "'\n";
+  for (auto& entry : shared_states_) {
+    ss << "shared_state[" << entry.first << "]='" << entry.second.data << "'\n";
+  }
+  ss << GetFinalFeatureTree()->DumpStateForTesting();
+  ss << "}StreamModel\n";
+  return ss.str();
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/stream_model.h b/chromium/components/feed/core/v2/stream_model.h
new file mode 100644
index 00000000000..2595ba228d3
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model.h
@@ -0,0 +1,152 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_STREAM_MODEL_H_
+#define COMPONENTS_FEED_CORE_V2_STREAM_MODEL_H_
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/containers/flat_map.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/proto/v2/wire/content_id.pb.h"
+#include "components/feed/core/v2/proto_util.h"
+#include "components/feed/core/v2/stream_model/ephemeral_change.h"
+#include "components/feed/core/v2/stream_model/feature_tree.h"
+
+namespace feedwire {
+class DataOperation;
+}  // namespace feedwire
+
+namespace feed {
+struct StreamModelUpdateRequest;
+
+// An in-memory stream model.
+class StreamModel {
+ public:
+  // Information about an update to the model.
+  struct UiUpdate {
+    struct SharedStateInfo {
+      // The shared state's unique ID.
+      std::string shared_state_id;
+      // Whether the shared state was just modified or added.
+      bool updated = false;
+    };
+    UiUpdate();
+    ~UiUpdate();
+    UiUpdate(const UiUpdate&);
+    UiUpdate& operator=(const UiUpdate&);
+    // Whether the list of content has changed. Use
+    // |StreamModel::GetContentList()| to get the updated list of content.
+    bool content_list_changed = false;
+    // The list of shared states in the model.
+    std::vector<SharedStateInfo> shared_states;
+  };
+
+  struct StoreUpdate {
+    StoreUpdate();
+    ~StoreUpdate();
+    StoreUpdate(const StoreUpdate&);
+    StoreUpdate(StoreUpdate&&);
+    StoreUpdate& operator=(const StoreUpdate&);
+    StoreUpdate& operator=(StoreUpdate&&);
+
+    int32_t sequence_number = 0;
+    std::vector<feedstore::DataOperation> operations;
+  };
+
+  class Observer {
+   public:
+    virtual ~Observer() = default;
+    // Called when the UI model changes.
+    virtual void OnUiUpdate(const UiUpdate& update) = 0;
+  };
+  class StoreObserver {
+   public:
+    // Called when the peristent store should be modified to reflect a model
+    // change.
+    virtual void OnStoreChange(const StoreUpdate& update) = 0;
+  };
+
+  StreamModel();
+  ~StreamModel();
+
+  StreamModel(const StreamModel& src) = delete;
+  StreamModel& operator=(const StreamModel&) = delete;
+
+  void SetObserver(Observer* observer);
+  void SetStoreObserver(StoreObserver* store_observer);
+
+  // Data access.
+
+  // Returns the full list of content in the order it should be presented.
+  const std::vector<ContentRevision>& GetContentList() const {
+    return content_list_;
+  }
+  // Returns a list of all shared state IDs.
+  std::vector<std::string> GetSharedStateIds() const;
+
+  // Apply an update from the network or storage.
+  void Update(std::unique_ptr<StreamModelUpdateRequest> update_request);
+
+  // Returns the content identified by |ContentRevision|.
+  const feedstore::Content* FindContent(ContentRevision revision) const;
+
+  // Returns the shared state data identified by |id|.
+  const std::string* FindSharedStateData(const std::string& id) const;
+
+  // Apply |operations| to the model.
+  void ExecuteOperations(std::vector<feedstore::DataOperation> operations);
+
+  // Create a temporary change that may be undone or committed later.
+  EphemeralChangeId CreateEphemeralChange(
+      std::vector<feedstore::DataOperation> operations);
+  // Commits a change. Returns false if the change does not exist.
+  bool CommitEphemeralChange(EphemeralChangeId id);
+  // Rejects a change. Returns false if the change does not exist.
+  bool RejectEphemeralChange(EphemeralChangeId id);
+
+  // Outputs a string representing the model state for debugging or testing.
+  std::string DumpStateForTesting();
+
+ private:
+  struct SharedState {
+    // Whether the data has been changed since the last call to |OnUiUpdate()|.
+    bool updated = true;
+    std::string data;
+  };
+  // The final feature tree after applying any ephemeral changes.
+  // May link directly to |base_feature_tree_|.
+  stream_model::FeatureTree* GetFinalFeatureTree();
+  const stream_model::FeatureTree* GetFinalFeatureTree() const;
+
+  void UpdateFlattenedTree();
+
+  Observer* observer_ = nullptr;  // Unowned.
+  StoreObserver* store_observer_ = nullptr;  // Unowned.
+  stream_model::ContentIdMap id_map_;
+  stream_model::FeatureTree base_feature_tree_{&id_map_};
+  // |base_feature_tree_| with |ephemeral_changes_| applied.
+  // Null if there are no ephemeral changes.
+  std::unique_ptr<stream_model::FeatureTree> feature_tree_after_changes_;
+  stream_model::EphemeralChangeList ephemeral_changes_;
+
+  // The following data is associated with the stream, but lives outside of the
+  // tree.
+
+  std::string next_page_token_;    // TODO(harringtond): use this value.
+  std::string consistency_token_;  // TODO(harringtond): use this value.
+  base::Time last_added_time_;     // TODO(harringtond): use this value.
+  base::flat_map<std::string, SharedState> shared_states_;
+  int32_t next_structure_sequence_number_ = 0;
+
+  // Current state of the flattened tree.
+  // Updated after each tree change.
+  std::vector<ContentRevision> content_list_;
+};
+
+}  // namespace feed
+#endif  // COMPONENTS_FEED_CORE_V2_STREAM_MODEL_H_
diff --git a/chromium/components/feed/core/v2/stream_model/README.md b/chromium/components/feed/core/v2/stream_model/README.md
new file mode 100644
index 00000000000..4f3f75bbe9b
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model/README.md
@@ -0,0 +1 @@
+This directory contains implementation details for StreamModel.
diff --git a/chromium/components/feed/core/v2/stream_model/ephemeral_change.cc b/chromium/components/feed/core/v2/stream_model/ephemeral_change.cc
new file mode 100644
index 00000000000..96e8a65a3ef
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model/ephemeral_change.cc
@@ -0,0 +1,64 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/stream_model/ephemeral_change.h"
+
+namespace feed {
+namespace stream_model {
+
+EphemeralChange::EphemeralChange(
+    EphemeralChangeId id,
+    std::vector<feedstore::DataOperation> operations)
+    : id_(id), operations_(std::move(operations)) {}
+EphemeralChange::~EphemeralChange() = default;
+
+EphemeralChangeList::EphemeralChangeList() = default;
+EphemeralChangeList::~EphemeralChangeList() = default;
+EphemeralChange* EphemeralChangeList::AddEphemeralChange(
+    std::vector<feedstore::DataOperation> operations) {
+  change_list_.push_back(std::make_unique<EphemeralChange>(
+      id_generator_.GenerateNextId(), operations));
+  return change_list_.back().get();
+}
+EphemeralChange* EphemeralChangeList::Find(EphemeralChangeId id) {
+  for (std::unique_ptr<EphemeralChange>& change : change_list_) {
+    if (change->id() == id)
+      return change.get();
+  }
+  return nullptr;
+}
+
+std::unique_ptr<FeatureTree> ApplyEphemeralChanges(
+    const FeatureTree& tree,
+    const EphemeralChangeList& changes) {
+  auto tree_with_changes = std::make_unique<FeatureTree>(&tree);
+
+  for (const std::unique_ptr<EphemeralChange>& change :
+       changes.GetChangeList()) {
+    for (const feedstore::DataOperation& operation : change->GetOperations()) {
+      if (operation.has_structure()) {
+        tree_with_changes->ApplyStreamStructure(operation.structure());
+      }
+      if (operation.has_content()) {
+        tree_with_changes->AddContent(operation.content());
+      }
+    }
+  }
+  return tree_with_changes;
+}
+
+std::unique_ptr<EphemeralChange> EphemeralChangeList::Remove(
+    EphemeralChangeId id) {
+  for (size_t i = 0; i < change_list_.size(); ++i) {
+    if (change_list_[i]->id() == id) {
+      std::unique_ptr<EphemeralChange> result = std::move(change_list_[i]);
+      change_list_.erase(change_list_.begin() + i);
+      return result;
+    }
+  }
+  return nullptr;
+}
+
+}  // namespace stream_model
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/stream_model/ephemeral_change.h b/chromium/components/feed/core/v2/stream_model/ephemeral_change.h
new file mode 100644
index 00000000000..fe293b3cb7b
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model/ephemeral_change.h
@@ -0,0 +1,66 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_STREAM_MODEL_EPHEMERAL_CHANGE_H_
+#define COMPONENTS_FEED_CORE_V2_STREAM_MODEL_EPHEMERAL_CHANGE_H_
+
+#include <memory>
+#include <vector>
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/v2/public/feed_stream_api.h"
+#include "components/feed/core/v2/stream_model/feature_tree.h"
+
+namespace feed {
+namespace stream_model {
+
+// A sequence of data operations that may be reverted.
+class EphemeralChange {
+ public:
+  EphemeralChange(EphemeralChangeId id,
+                  std::vector<feedstore::DataOperation> operations);
+  ~EphemeralChange();
+  EphemeralChange(const EphemeralChange&) = delete;
+  EphemeralChange& operator=(const EphemeralChange&) = delete;
+
+  EphemeralChangeId id() const { return id_; }
+  const std::vector<feedstore::DataOperation>& GetOperations() const {
+    return operations_;
+  }
+  std::vector<feedstore::DataOperation>& GetOperations() { return operations_; }
+
+ private:
+  EphemeralChangeId id_;
+  std::vector<feedstore::DataOperation> operations_;
+};
+
+// A list of |EphemeralChange| objects.
+class EphemeralChangeList {
+ public:
+  EphemeralChangeList();
+  ~EphemeralChangeList();
+  EphemeralChangeList(const EphemeralChangeList&) = delete;
+  EphemeralChangeList& operator=(const EphemeralChangeList&) = delete;
+
+  const std::vector<std::unique_ptr<EphemeralChange>>& GetChangeList() const {
+    return change_list_;
+  }
+  EphemeralChange* Find(EphemeralChangeId id);
+  EphemeralChange* AddEphemeralChange(
+      std::vector<feedstore::DataOperation> operations);
+  std::unique_ptr<EphemeralChange> Remove(EphemeralChangeId id);
+
+ private:
+  EphemeralChangeId::Generator id_generator_;
+  std::vector<std::unique_ptr<EphemeralChange>> change_list_;
+};
+
+// Return a new |FeatureTree| by applying |changes| to |tree|.
+std::unique_ptr<FeatureTree> ApplyEphemeralChanges(
+    const FeatureTree& tree,
+    const EphemeralChangeList& changes);
+
+}  // namespace stream_model
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_STREAM_MODEL_EPHEMERAL_CHANGE_H_
diff --git a/chromium/components/feed/core/v2/stream_model/feature_tree.cc b/chromium/components/feed/core/v2/stream_model/feature_tree.cc
new file mode 100644
index 00000000000..5c8373a77e3
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model/feature_tree.cc
@@ -0,0 +1,223 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/stream_model/feature_tree.h"
+
+#include <algorithm>
+#include <sstream>
+
+#include "base/logging.h"
+
+namespace feed {
+namespace stream_model {
+
+ContentIdMap::ContentIdMap() = default;
+ContentIdMap::~ContentIdMap() = default;
+
+ContentTag ContentIdMap::GetContentTag(const feedwire::ContentId& id) {
+  auto iter = mapping_.find(id);
+  if (iter != mapping_.end())
+    return iter->second;
+  ContentTag tag = tag_generator_.GenerateNextId();
+  mapping_[id] = tag;
+  return tag;
+}
+
+ContentRevision ContentIdMap::NextContentRevision() {
+  return revision_generator_.GenerateNextId();
+}
+
+StreamNode::StreamNode() = default;
+StreamNode::~StreamNode() = default;
+StreamNode::StreamNode(const StreamNode&) = default;
+StreamNode& StreamNode::operator=(const StreamNode&) = default;
+
+FeatureTree::FeatureTree(ContentIdMap* id_map) : id_map_(id_map) {}
+
+FeatureTree::FeatureTree(const FeatureTree* base)
+    : base_(base),
+      id_map_(base->id_map_),
+      computed_root_(base->computed_root_),
+      root_tag_(base->root_tag_),
+      nodes_(base->nodes_) {}
+FeatureTree::~FeatureTree() = default;
+
+StreamNode* FeatureTree::GetOrMakeNode(ContentTag id) {
+  ResizeNodesIfNeeded(id);
+  return &nodes_[id.value()];
+}
+
+const StreamNode* FeatureTree::FindNode(ContentTag id) const {
+  return const_cast<FeatureTree*>(this)->FindNode(id);
+}
+
+StreamNode* FeatureTree::FindNode(ContentTag id) {
+  if (!id.is_null() && nodes_.size() > id.value())
+    return &nodes_[id.value()];
+  return nullptr;
+}
+
+const feedstore::Content* FeatureTree::FindContent(ContentRevision id) const {
+  auto iter = content_.find(id);
+  if (iter != content_.end())
+    return &iter->second;
+  return base_ ? base_->FindContent(id) : nullptr;
+}
+
+void FeatureTree::ApplyStreamStructure(
+    const feedstore::StreamStructure& structure) {
+  switch (structure.operation()) {
+    case feedstore::StreamStructure::CLEAR_ALL:
+      nodes_.clear();
+      content_.clear();
+      computed_root_ = false;
+      break;
+    case feedstore::StreamStructure::UPDATE_OR_APPEND: {
+      const ContentTag child_id = GetContentTag(structure.content_id());
+      const bool is_stream =
+          structure.type() == feedstore::StreamStructure::STREAM;
+      ContentTag parent_id;
+      if (structure.has_parent_id()) {
+        parent_id = GetContentTag(structure.parent_id());
+      }
+      ResizeNodesIfNeeded(std::max(child_id, parent_id));
+      StreamNode& child = nodes_[child_id.value()];
+      StreamNode* parent = FindNode(parent_id);
+
+      // If a node already has a parent, treat this as an update, not an append
+      // operation.
+      child.is_stream = is_stream;
+      child.tombstoned = false;
+      if (root_tag_ == child_id) {
+        computed_root_ = false;
+      }
+
+      if (parent && !child.has_parent) {
+        // The child doesn't yet have a parent, but it should. Link to the
+        // parent now. If the child already has a parent, we will never change
+        // the parent even if requested by UPDATE_OR_APPEND.
+        child.has_parent = true;
+        child.previous_sibling = parent->last_child;
+        parent->last_child = child_id;
+      } else if (!parent && is_stream) {
+        // The node meets the criteria for root.
+        computed_root_ = true;
+        root_tag_ = child_id;
+      }
+    } break;
+    case feedstore::StreamStructure::REMOVE: {
+      // Removal is just unlinking the node from the tree.
+      // If it's added back again later, it retains its old children.
+      ContentTag tag = GetContentTag(structure.content_id());
+      if (root_tag_ == tag) {
+        computed_root_ = false;
+      }
+      GetOrMakeNode(tag)->tombstoned = true;
+    } break;
+    default:
+      break;
+  }
+}  // namespace stream_model
+
+void FeatureTree::ResizeNodesIfNeeded(ContentTag id) {
+  if (nodes_.size() <= id.value())
+    nodes_.resize(id.value() + 1);
+}
+
+void FeatureTree::AddContent(feedstore::Content content) {
+  AddContent(id_map_->NextContentRevision(), std::move(content));
+}
+
+void FeatureTree::AddContent(ContentRevision revision_id,
+                             feedstore::Content content) {
+  // TODO(harringtond): Consider de-duping content.
+  // Currently, we copy content for ephemeral changes. Both when the ephemeral
+  // change is created, and when it is committed. We should consider eliminating
+  // these copies.
+  const ContentTag tag = GetContentTag(content.content_id());
+  DCHECK(!content_.count(revision_id));
+  GetOrMakeNode(tag)->content_revision = revision_id;
+  content_[revision_id] = std::move(content);
+}
+
+void FeatureTree::ResolveRoot() {
+  if (computed_root_) {
+    DCHECK(!FindNode(root_tag_) || FindNode(root_tag_)->is_stream) << root_tag_;
+    DCHECK(!FindNode(root_tag_) || !FindNode(root_tag_)->tombstoned);
+    DCHECK(!FindNode(root_tag_) || !FindNode(root_tag_)->has_parent);
+    return;
+  }
+  root_tag_ = ContentTag();
+  for (size_t i = 0; i < nodes_.size(); ++i) {
+    const StreamNode& node = nodes_[i];
+    if (node.is_stream && !node.tombstoned && !node.has_parent) {
+      root_tag_ = ContentTag(i);
+    }
+  }
+  computed_root_ = true;
+}
+
+std::vector<ContentRevision> FeatureTree::GetVisibleContent() {
+  ResolveRoot();
+  std::vector<ContentRevision> result;
+  std::vector<ContentTag> stack;
+
+  // Node: Cycles are impossible here. The root node is guaranteed to
+  // not be a child. All other nodes have exactly one parent.
+  // It is possible for nodes to cycle, like A->B->A, but in this case there can
+  // be no valid root because all nodes have a parent.
+  stack.push_back(root_tag_);
+  while (!stack.empty()) {
+    const ContentTag tag = stack.back();
+    stack.pop_back();
+    const StreamNode* node = FindNode(tag);
+    if (!node || node->tombstoned)
+      continue;
+    if (!node->last_child.is_null()) {
+      for (ContentTag child_id = node->last_child; !child_id.is_null();
+           child_id = nodes_[child_id.value()].previous_sibling) {
+        stack.push_back(child_id);
+      }
+    }
+    if (!node->content_revision.is_null()) {
+      result.push_back(node->content_revision);
+    }
+  }
+  return result;
+}
+
+std::string FeatureTree::DumpStateForTesting() {
+  std::stringstream ss;
+  ss << "FeatureTree{\n";
+  ResolveRoot();
+  std::vector<std::pair<int, ContentTag>> stack;
+
+  stack.push_back({1, root_tag_});
+  while (!stack.empty()) {
+    const ContentTag tag = stack.back().second;
+    const int depth = stack.back().first;
+    stack.pop_back();
+    const StreamNode* node = FindNode(tag);
+    if (!node || node->tombstoned)
+      continue;
+    ss << std::string(depth, ' ') << "|-";
+    ss << (node->is_stream ? "ROOT" : "node");
+    if (!node->last_child.is_null()) {
+      for (ContentTag child_id = node->last_child; !child_id.is_null();
+           child_id = nodes_[child_id.value()].previous_sibling) {
+        stack.push_back({depth + 1, child_id});
+      }
+    }
+    if (!node->content_revision.is_null()) {
+      const feedstore::Content* content = FindContent(node->content_revision);
+      ss << " content.frame=" << content->frame();
+    }
+    ss << '\n';
+  }
+  ss << "}FeatureTree\n";
+  return ss.str();
+}
+
+}  // namespace stream_model
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/stream_model/feature_tree.h b/chromium/components/feed/core/v2/stream_model/feature_tree.h
new file mode 100644
index 00000000000..2aa79e8bd6c
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model/feature_tree.h
@@ -0,0 +1,137 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_STREAM_MODEL_FEATURE_TREE_H_
+#define COMPONENTS_FEED_CORE_V2_STREAM_MODEL_FEATURE_TREE_H_
+
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/util/type_safety/id_type.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/v2/proto_util.h"
+#include "components/feed/core/v2/public/feed_stream_api.h"
+
+namespace feed {
+namespace stream_model {
+
+// Uniquely identifies a feedwire::ContentId. Provided by |ContentIdMap|.
+using ContentTag = util::IdTypeU32<class ContentTagClass>;
+using ContentRevision = feed::ContentRevision;
+
+// Maps ContentId into ContentTag, and generates ContentRevision IDs.
+class ContentIdMap {
+ public:
+  ContentIdMap();
+  ~ContentIdMap();
+  ContentIdMap(const ContentIdMap&) = delete;
+  ContentIdMap& operator=(const ContentIdMap&) = delete;
+
+  ContentTag GetContentTag(const feedwire::ContentId& id);
+  ContentRevision NextContentRevision();
+
+ private:
+  ContentTag::Generator tag_generator_;
+  ContentRevision::Generator revision_generator_;
+  std::map<feedwire::ContentId, ContentTag, ContentIdCompareFunctor> mapping_;
+};
+
+// A node in FeatureTree.
+struct StreamNode {
+  StreamNode();
+  ~StreamNode();
+  StreamNode(const StreamNode&);
+  StreamNode& operator=(const StreamNode&);
+  // If true, this nodes has been removed and should be ignored.
+  bool tombstoned = false;
+  // Whether this is a STREAM node.
+  bool is_stream = false;
+  // Whether this node has a parent.
+  bool has_parent = false;
+  // If this node has content, this identifies it.
+  ContentRevision content_revision;
+  // Child relations are stored in linked-list fashion.
+  // The ID of the last child, or null.
+  ContentTag last_child;
+  // The ID of the sibling before this one.
+  ContentTag previous_sibling;
+};
+
+// The feature tree which underlies StreamModel.
+// This tree is different that most, the rules are as follows:
+// * A node may or may not have a parent, so this is more of a forest than a
+//   tree.
+// * When nodes are removed, their set of children are remembered. If the node
+//   is added again, it retains its old children.
+// * A node can be added multiple times, but subsequent adds will not change
+//   the node's parent.
+// * There is only one 'stream root' acknowledged, even though there can be many
+//   roots. The stream root is the last root node added of type STREAM. The
+//   stream root identifies the tree whose nodes are used to compute
+//   |GetVisibleContent()|.
+// * A tree can be constructed with a base tree. This copies features from base,
+//   but refers to content stored in base by reference.
+class FeatureTree {
+ public:
+  // Constructor. |id_map| is retained by FeatureTree, and must have a greater
+  // scope than FeatureTree.
+  explicit FeatureTree(ContentIdMap* id_map);
+  // Create a |FeatureTree| which starts as a copy of |base|.
+  // Copies structure from |base|, and keeps a reference for content access.
+  explicit FeatureTree(const FeatureTree* base);
+  ~FeatureTree();
+
+  FeatureTree(const FeatureTree& src) = delete;
+  FeatureTree& operator=(const FeatureTree& src) = delete;
+
+  // Mutations.
+
+  void ApplyStreamStructure(const feedstore::StreamStructure& structure);
+  void AddContent(feedstore::Content content);
+  void AddContent(ContentRevision revision_id, feedstore::Content content);
+
+  // Data access.
+
+  const StreamNode* FindNode(ContentTag id) const;
+  StreamNode* FindNode(ContentTag id);
+  const feedstore::Content* FindContent(ContentRevision id) const;
+  ContentTag GetContentTag(const feedwire::ContentId& id) {
+    return id_map_->GetContentTag(id);
+  }
+
+  // Returns the list of content that should be visible.
+  std::vector<ContentRevision> GetVisibleContent();
+
+  std::string DumpStateForTesting();
+
+ private:
+  StreamNode* GetOrMakeNode(ContentTag id);
+  void ResolveRoot();
+  void ResizeNodesIfNeeded(ContentTag id);
+  void RemoveFromParent(ContentTag node_id);
+  bool RemoveFromParent(StreamNode* parent, ContentTag node_id);
+
+  const FeatureTree* base_ = nullptr;  // Unowned.
+  ContentIdMap* id_map_;               // Unowned.
+  // Finding the root:
+  // We pick the root node as the last STREAM node which has no parent.
+  // In most cases, we can identify the root as the tree is built.
+  // But in some cases, we need to search all nodes to find the root.
+  // |computed_root_| is true if |root_tag_| is guaranteed to identify the root.
+  bool computed_root_ = true;
+  ContentTag root_tag_;
+  // All nodes in the forest, included removed nodes.
+  // This datastructure was selected to make copies efficient.
+  std::vector<StreamNode> nodes_;
+  // TODO(harringtond): It may be possible to remove old revisions of content
+  // to save memory.
+  std::map<ContentRevision, feedstore::Content> content_;
+};
+
+}  // namespace stream_model
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_STREAM_MODEL_FEATURE_TREE_H_
diff --git a/chromium/components/feed/core/v2/stream_model_unittest.cc b/chromium/components/feed/core/v2/stream_model_unittest.cc
new file mode 100644
index 00000000000..d3a0b4c2825
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model_unittest.cc
@@ -0,0 +1,449 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/stream_model.h"
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/optional.h"
+#include "base/strings/string_number_conversions.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/proto/v2/wire/content_id.pb.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+#include "components/feed/core/v2/test/stream_builder.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace feed {
+namespace {
+using StoreUpdate = StreamModel::StoreUpdate;
+using UiUpdate = StreamModel::UiUpdate;
+
+std::vector<std::string> GetContentFrames(const StreamModel& model) {
+  std::vector<std::string> frames;
+  for (ContentRevision rev : model.GetContentList()) {
+    const feedstore::Content* content = model.FindContent(rev);
+    if (content) {
+      frames.push_back(content->frame());
+    } else {
+      frames.push_back("<null>");
+    }
+  }
+  return frames;
+}
+
+class TestObserver : public StreamModel::Observer {
+ public:
+  explicit TestObserver(StreamModel* model) { model->SetObserver(this); }
+
+  // StreamModel::Observer.
+  void OnUiUpdate(const UiUpdate& update) override { update_ = update; }
+  const base::Optional<UiUpdate>& GetUiUpdate() const { return update_; }
+  bool ContentListChanged() const {
+    return update_ && update_->content_list_changed;
+  }
+
+  void Clear() { update_ = base::nullopt; }
+
+ private:
+  base::Optional<UiUpdate> update_;
+};
+
+class TestStoreObserver : public StreamModel::StoreObserver {
+ public:
+  explicit TestStoreObserver(StreamModel* model) {
+    model->SetStoreObserver(this);
+  }
+
+  // StreamModel::StoreObserver.
+  void OnStoreChange(const StoreUpdate& records) override { update_ = records; }
+
+  const base::Optional<StoreUpdate>& GetUpdate() const { return update_; }
+
+  void Clear() { update_ = base::nullopt; }
+
+ private:
+  base::Optional<StoreUpdate> update_;
+};
+
+TEST(StreamModelTest, ConstructEmptyModel) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  EXPECT_EQ(0UL, model.GetContentList().size());
+}
+
+TEST(StreamModelTest, ExecuteOperationsTypicalStream) {
+  StreamModel model;
+  TestObserver observer(&model);
+  TestStoreObserver store_observer(&model);
+
+  model.ExecuteOperations(MakeTypicalStreamOperations());
+  EXPECT_TRUE(observer.ContentListChanged());
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+  ASSERT_TRUE(store_observer.GetUpdate());
+  ASSERT_EQ(MakeTypicalStreamOperations().size(),
+            store_observer.GetUpdate()->operations.size());
+}
+
+TEST(StreamModelTest, AddContentWithoutRoot) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations{
+      MakeOperation(MakeCluster(0, MakeRootId())),
+      MakeOperation(MakeContentNode(0, MakeClusterId(0))),
+      MakeOperation(MakeContent(0)),
+  };
+  model.ExecuteOperations(operations);
+
+  // Without a root, no content is visible.
+  EXPECT_EQ(std::vector<std::string>({}), GetContentFrames(model));
+}
+
+// Verify Stream -> Content works.
+TEST(StreamModelTest, AddStreamContent) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations{
+      MakeOperation(MakeStream()),
+      MakeOperation(MakeContentNode(0, MakeRootId())),
+      MakeOperation(MakeContent(0)),
+  };
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({"f:0"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, AddRootAsChild) {
+  // When the root is added as a child, it's no longer considered a root.
+  StreamModel model;
+  TestObserver observer(&model);
+  feedstore::StreamStructure stream_with_parent = MakeStream();
+  *stream_with_parent.mutable_parent_id() = MakeContentContentId(0);
+  std::vector<feedstore::DataOperation> operations{
+      MakeOperation(MakeStream()),
+      MakeOperation(MakeContentNode(0, MakeRootId())),
+      MakeOperation(MakeContent(0)),
+      MakeOperation(stream_with_parent),
+  };
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({}), GetContentFrames(model));
+}
+
+// Changing the STREAM root to CLUSTER means it is no longer eligible to be
+// the root.
+TEST(StreamModelTest, ChangeStreamToCluster) {
+  StreamModel model;
+  TestObserver observer(&model);
+  feedstore::StreamStructure stream_as_cluster = MakeStream();
+  stream_as_cluster.set_type(feedstore::StreamStructure::CLUSTER);
+
+  std::vector<feedstore::DataOperation> operations{
+      MakeOperation(MakeStream()),
+      MakeOperation(MakeContentNode(0, MakeRootId())),
+      MakeOperation(MakeContent(0)),
+      MakeOperation(stream_as_cluster),
+  };
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RemoveCluster) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeRemove(MakeClusterId(0))));
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({"f:1"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RemoveContent) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeRemove(MakeContentContentId(0))));
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({"f:1"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RemoveRoot) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeRemove(MakeRootId())));
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>(), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RemoveAndAddRoot) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeRemove(MakeRootId())));
+  operations.push_back(MakeOperation(MakeStream()));
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, SwitchStreams) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeStream(2)));
+  operations.push_back(MakeOperation(MakeContentNode(9, MakeRootId(2))));
+  operations.push_back(MakeOperation(MakeContent(9)));
+
+  model.ExecuteOperations(operations);
+
+  // The last stream added becomes the root, so only children of 'root2' are
+  // included.
+  EXPECT_EQ(std::vector<std::string>({"f:9"}), GetContentFrames(model));
+
+  // Adding the original stream back will re-activate it.
+  model.ExecuteOperations({MakeOperation(MakeStream())});
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+
+  // Removing 'root' will now make 'root2' active again.
+  model.ExecuteOperations({MakeOperation(MakeRemove(MakeRootId()))});
+  EXPECT_EQ(std::vector<std::string>({"f:9"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RemoveAndUpdateCluster) {
+  // Remove a cluster and add it back. Adding it back keeps its original
+  // placement.
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeRemove(MakeClusterId(0))));
+  operations.push_back(MakeOperation(MakeCluster(0, MakeRootId())));
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RemoveAndAppendToNewParent) {
+  // Attempt to re-parent a node. This is not allowed, the old parent remains.
+  StreamModel model;
+  TestObserver observer(&model);
+
+  std::vector<feedstore::DataOperation> operations =
+      MakeTypicalStreamOperations();
+  operations.push_back(MakeOperation(MakeRemove(MakeClusterId(0))));
+  operations.push_back(MakeOperation(MakeCluster(0, MakeClusterId(1))));
+
+  model.ExecuteOperations(operations);
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, EphemeralNewCluster) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  model.ExecuteOperations(MakeTypicalStreamOperations());
+  observer.Clear();
+
+  model.CreateEphemeralChange({
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  });
+
+  EXPECT_TRUE(observer.ContentListChanged());
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1", "f:2"}),
+            GetContentFrames(model));
+}
+
+TEST(StreamModelTest, CommitEphemeralChange) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  model.ExecuteOperations(MakeTypicalStreamOperations());
+
+  EphemeralChangeId change_id = model.CreateEphemeralChange({
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  });
+
+  observer.Clear();
+  TestStoreObserver store_observer(&model);
+  EXPECT_TRUE(model.CommitEphemeralChange(change_id));
+
+  // Check that the observer's |OnStoreChange()| was called.
+  ASSERT_TRUE(store_observer.GetUpdate());
+  StoreUpdate store_update = *store_observer.GetUpdate();
+  ASSERT_EQ(3UL, store_update.operations.size());
+  EXPECT_EQ(feedstore::StreamStructure::CLUSTER,
+            store_update.operations[0].structure().type());
+  EXPECT_EQ(feedstore::StreamStructure::CONTENT,
+            store_update.operations[1].structure().type());
+
+  // Can't reject after commit.
+  EXPECT_FALSE(model.RejectEphemeralChange(change_id));
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1", "f:2"}),
+            GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RejectEphemeralChange) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  model.ExecuteOperations(MakeTypicalStreamOperations());
+  EphemeralChangeId change_id = model.CreateEphemeralChange({
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  });
+  observer.Clear();
+
+  EXPECT_TRUE(model.RejectEphemeralChange(change_id));
+  EXPECT_TRUE(observer.ContentListChanged());
+  // Can't commit after reject.
+  EXPECT_FALSE(model.CommitEphemeralChange(change_id));
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+}
+
+TEST(StreamModelTest, RejectFirstEphemeralChange) {
+  StreamModel model;
+  TestObserver observer(&model);
+
+  model.ExecuteOperations(MakeTypicalStreamOperations());
+  EphemeralChangeId change_id1 = model.CreateEphemeralChange({
+      MakeOperation(MakeCluster(2, MakeRootId())),
+      MakeOperation(MakeContentNode(2, MakeClusterId(2))),
+      MakeOperation(MakeContent(2)),
+  });
+
+  model.CreateEphemeralChange({
+      MakeOperation(MakeCluster(3, MakeRootId())),
+      MakeOperation(MakeContentNode(3, MakeClusterId(3))),
+      MakeOperation(MakeContent(3)),
+  });
+  observer.Clear();
+
+  EXPECT_TRUE(model.RejectEphemeralChange(change_id1));
+  EXPECT_TRUE(observer.ContentListChanged());
+  // Can't commit after reject.
+  EXPECT_FALSE(model.CommitEphemeralChange(change_id1));
+
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1", "f:3"}),
+            GetContentFrames(model));
+}
+
+TEST(StreamModelTest, InitialLoad) {
+  StreamModel model;
+  TestObserver observer(&model);
+  TestStoreObserver store_observer(&model);
+  model.Update(MakeTypicalInitialModelState());
+
+  // Check that content was added and the store doesn't receive its own update.
+  EXPECT_TRUE(observer.ContentListChanged());
+  EXPECT_EQ(std::vector<std::string>({"f:0", "f:1"}), GetContentFrames(model));
+  ASSERT_EQ(1UL, observer.GetUiUpdate()->shared_states.size());
+  EXPECT_NE("", observer.GetUiUpdate()->shared_states[0].shared_state_id);
+  const std::string* shared_state_data = model.FindSharedStateData(
+      observer.GetUiUpdate()->shared_states[0].shared_state_id);
+  ASSERT_TRUE(shared_state_data);
+  EXPECT_EQ("ss:0", *shared_state_data);
+  EXPECT_FALSE(store_observer.GetUpdate());
+}
+
+TEST(StreamModelTest, StoreObserverReceivesIncreasingSequenceNumbers) {
+  StreamModel model;
+  TestObserver observer(&model);
+  TestStoreObserver store_observer(&model);
+
+  // Initialize the model starting at sequence number 5.
+  {
+    std::unique_ptr<StreamModelUpdateRequest> initial_state =
+        MakeTypicalInitialModelState();
+    initial_state->max_structure_sequence_number = 5;
+    model.Update(std::move(initial_state));
+  }
+
+  model.ExecuteOperations({MakeOperation(MakeRemove(MakeContentContentId(0)))});
+
+  ASSERT_TRUE(store_observer.GetUpdate());
+  EXPECT_EQ(6, store_observer.GetUpdate()->sequence_number);
+
+  store_observer.Clear();
+  model.ExecuteOperations({MakeOperation(MakeRemove(MakeContentContentId(0)))});
+
+  ASSERT_TRUE(store_observer.GetUpdate());
+  EXPECT_EQ(7, store_observer.GetUpdate()->sequence_number);
+}
+
+TEST(StreamModelTest, SharedStateCanBeAddedOnlyOnce) {
+  StreamModel model;
+  TestObserver observer(&model);
+  TestStoreObserver store_observer(&model);
+
+  // Update the model twice with this request. The shared state should not
+  // be added the second time.
+  StreamModelUpdateRequest update_request;
+  update_request.source =
+      StreamModelUpdateRequest::Source::kInitialLoadFromStore;
+  update_request.content.push_back(MakeContent(0));
+  update_request.stream_structures = {MakeStream(),
+                                      MakeCluster(0, MakeRootId()),
+                                      MakeContentNode(0, MakeClusterId(0))};
+  update_request.shared_states.push_back(MakeSharedState(0));
+
+  model.Update(std::make_unique<StreamModelUpdateRequest>(update_request));
+  observer.Clear();
+  model.Update(std::make_unique<StreamModelUpdateRequest>(update_request));
+  ASSERT_EQ(1UL, observer.GetUiUpdate()->shared_states.size());
+  EXPECT_FALSE(observer.GetUiUpdate()->shared_states[0].updated);
+}
+
+TEST(StreamModelTest, ClearAllErasesSharedStates) {
+  StreamModel model;
+  TestObserver observer(&model);
+  TestStoreObserver store_observer(&model);
+  // CLEAR_ALL is the first operation in the typical initial model state.
+  // The second Update() will therefore need to remove and add the shared
+  // state.
+  model.Update(MakeTypicalInitialModelState());
+  observer.Clear();
+  model.Update(MakeTypicalInitialModelState());
+
+  ASSERT_EQ(1UL, observer.GetUiUpdate()->shared_states.size());
+  EXPECT_TRUE(observer.GetUiUpdate()->shared_states[0].updated);
+}
+
+}  // namespace
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/stream_model_update_request.cc b/chromium/components/feed/core/v2/stream_model_update_request.cc
new file mode 100644
index 00000000000..1cd8d8d77fc
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model_update_request.cc
@@ -0,0 +1,255 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/stream_model_update_request.h"
+
+#include <utility>
+
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "components/feed/core/proto/v2/wire/data_operation.pb.h"
+#include "components/feed/core/proto/v2/wire/feature.pb.h"
+#include "components/feed/core/proto/v2/wire/feed_response.pb.h"
+#include "components/feed/core/proto/v2/wire/payload_metadata.pb.h"
+#include "components/feed/core/proto/v2/wire/stream_structure.pb.h"
+#include "components/feed/core/proto/v2/wire/token.pb.h"
+#include "components/feed/core/v2/proto_util.h"
+
+namespace feed {
+
+namespace {
+
+feedstore::StreamStructure::Operation TranslateOperationType(
+    feedwire::DataOperation::Operation operation) {
+  switch (operation) {
+    case feedwire::DataOperation::UNKNOWN_OPERATION:
+      return feedstore::StreamStructure::UNKNOWN;
+    case feedwire::DataOperation::CLEAR_ALL:
+      return feedstore::StreamStructure::CLEAR_ALL;
+    case feedwire::DataOperation::UPDATE_OR_APPEND:
+      return feedstore::StreamStructure::UPDATE_OR_APPEND;
+    case feedwire::DataOperation::REMOVE:
+      return feedstore::StreamStructure::REMOVE;
+    default:
+      return feedstore::StreamStructure::UNKNOWN;
+  }
+}
+
+feedstore::StreamStructure::Type TranslateNodeType(
+    feedwire::Feature::RenderableUnit renderable_unit) {
+  switch (renderable_unit) {
+    case feedwire::Feature::UNKNOWN_RENDERABLE_UNIT:
+      return feedstore::StreamStructure::UNKNOWN_TYPE;
+    case feedwire::Feature::STREAM:
+      return feedstore::StreamStructure::STREAM;
+    case feedwire::Feature::CONTENT:
+      return feedstore::StreamStructure::CONTENT;
+    case feedwire::Feature::CLUSTER:
+      return feedstore::StreamStructure::CLUSTER;
+    default:
+      return feedstore::StreamStructure::UNKNOWN_TYPE;
+  }
+}
+
+struct ConvertedDataOperation {
+  bool has_stream_structure = false;
+  feedstore::StreamStructure stream_structure;
+  bool has_content = false;
+  feedstore::Content content;
+  bool has_shared_state = false;
+  feedstore::StreamSharedState shared_state;
+};
+
+bool TranslateFeature(feedwire::Feature* feature,
+                      ConvertedDataOperation* result) {
+  feedstore::StreamStructure::Type type =
+      TranslateNodeType(feature->renderable_unit());
+  result->stream_structure.set_type(type);
+
+  if (type == feedstore::StreamStructure::CONTENT) {
+    feedwire::Content* wire_content = feature->mutable_content_extension();
+
+    if (wire_content->type() != feedwire::Content::XSURFACE)
+      return false;
+
+    // TODO(iwells): We still need score, availability_time_seconds,
+    // offline_metadata, and representation_data to populate content_info.
+
+    *(result->content.mutable_content_id()) =
+        result->stream_structure.content_id();
+    result->content.set_allocated_frame(
+        wire_content->mutable_xsurface_content()->release_xsurface_output());
+    result->has_content = true;
+  }
+  return true;
+}
+
+base::Optional<feedstore::StreamSharedState> TranslateSharedState(
+    feedwire::ContentId content_id,
+    feedwire::RenderData* wire_shared_state) {
+  if (wire_shared_state->render_data_type() != feedwire::RenderData::XSURFACE) {
+    return base::nullopt;
+  }
+
+  feedstore::StreamSharedState shared_state;
+  *shared_state.mutable_content_id() = std::move(content_id);
+  shared_state.set_allocated_shared_state_data(
+      wire_shared_state->mutable_xsurface_container()->release_render_data());
+  return shared_state;
+}
+
+bool TranslatePayload(feedwire::DataOperation operation,
+                      ConvertedDataOperation* result) {
+  switch (operation.payload_case()) {
+    case feedwire::DataOperation::kFeature: {
+      feedwire::Feature* feature = operation.mutable_feature();
+      result->stream_structure.set_allocated_parent_id(
+          feature->release_parent_id());
+
+      if (!TranslateFeature(feature, result))
+        return false;
+    } break;
+    case feedwire::DataOperation::kNextPageToken: {
+      feedwire::Token* token = operation.mutable_next_page_token();
+      result->stream_structure.set_allocated_parent_id(
+          token->release_parent_id());
+      // TODO(iwells): We should be setting token bytes here.
+      // result->stream_structure.set_allocated_next_page_token(
+      //   token->MutableExtension(
+      //     components::feed::core::proto::ui
+      //       ::stream::NextPageToken::next_page_token_extension
+      //   )->release_next_page_token());
+    } break;
+    case feedwire::DataOperation::kRenderData: {
+      base::Optional<feedstore::StreamSharedState> shared_state =
+          TranslateSharedState(result->stream_structure.content_id(),
+                               operation.mutable_render_data());
+      if (!shared_state)
+        return false;
+
+      result->shared_state = std::move(shared_state.value());
+      result->has_shared_state = true;
+    } break;
+    // Fall through
+    case feedwire::DataOperation::kInPlaceUpdateHandle:
+    case feedwire::DataOperation::kTemplates:
+    case feedwire::DataOperation::PAYLOAD_NOT_SET:
+    default:
+      return false;
+  }
+
+  return true;
+}
+
+base::Optional<ConvertedDataOperation> TranslateDataOperationInternal(
+    feedwire::DataOperation operation) {
+  feedstore::StreamStructure::Operation operation_type =
+      TranslateOperationType(operation.operation());
+
+  ConvertedDataOperation result;
+  result.stream_structure.set_operation(operation_type);
+  result.has_stream_structure = true;
+
+  switch (operation_type) {
+    case feedstore::StreamStructure::CLEAR_ALL:
+      return result;
+
+    case feedstore::StreamStructure::UPDATE_OR_APPEND:
+      if (!operation.has_metadata() || !operation.metadata().has_content_id())
+        return base::nullopt;
+
+      result.stream_structure.set_allocated_content_id(
+          operation.mutable_metadata()->release_content_id());
+
+      if (!TranslatePayload(std::move(operation), &result))
+        return base::nullopt;
+      break;
+
+    case feedstore::StreamStructure::REMOVE:
+      if (!operation.has_metadata() || !operation.metadata().has_content_id())
+        return base::nullopt;
+
+      result.stream_structure.set_allocated_content_id(
+          operation.mutable_metadata()->release_content_id());
+      break;
+
+    case feedstore::StreamStructure::UNKNOWN:  // Fall through
+    default:
+      return base::nullopt;
+  }
+
+  return result;
+}
+
+}  // namespace
+
+StreamModelUpdateRequest::StreamModelUpdateRequest() = default;
+StreamModelUpdateRequest::~StreamModelUpdateRequest() = default;
+StreamModelUpdateRequest::StreamModelUpdateRequest(
+    const StreamModelUpdateRequest&) = default;
+StreamModelUpdateRequest& StreamModelUpdateRequest::operator=(
+    const StreamModelUpdateRequest&) = default;
+
+base::Optional<feedstore::DataOperation> TranslateDataOperation(
+    feedwire::DataOperation wire_operation) {
+  feedstore::DataOperation store_operation;
+  base::Optional<ConvertedDataOperation> converted =
+      TranslateDataOperationInternal(std::move(wire_operation));
+  if (!converted)
+    return base::nullopt;
+
+  if (!converted->has_stream_structure && !converted->has_content)
+    return base::nullopt;
+
+  *store_operation.mutable_structure() = std::move(converted->stream_structure);
+  *store_operation.mutable_content() = std::move(converted->content);
+  return store_operation;
+}
+
+std::unique_ptr<StreamModelUpdateRequest> TranslateWireResponse(
+    feedwire::Response response,
+    base::TimeDelta response_time,
+    base::Time current_time) {
+  if (response.response_version() != feedwire::Response::FEED_RESPONSE)
+    return nullptr;
+
+  auto result = std::make_unique<StreamModelUpdateRequest>();
+
+  feedwire::FeedResponse* feed_response = response.mutable_feed_response();
+  for (auto& wire_data_operation : *feed_response->mutable_data_operation()) {
+    if (!wire_data_operation.has_operation())
+      continue;
+
+    base::Optional<ConvertedDataOperation> operation =
+        TranslateDataOperationInternal(std::move(wire_data_operation));
+    if (!operation)
+      continue;
+
+    if (operation->has_stream_structure) {
+      result->stream_structures.push_back(
+          std::move(operation->stream_structure));
+    }
+
+    if (operation->has_content)
+      result->content.push_back(std::move(operation.value().content));
+
+    if (operation->has_shared_state)
+      result->shared_states.push_back(std::move(operation->shared_state));
+  }
+
+  // TODO(harringtond): If there's more than one shared state, record some
+  // sort of error.
+  if (!result->shared_states.empty()) {
+    *result->stream_data.mutable_shared_state_id() =
+        result->shared_states.front().content_id();
+  }
+  feedstore::SetLastAddedTime(current_time, &result->stream_data);
+  result->server_response_time =
+      feed_response->feed_response_metadata().response_time_ms();
+  result->response_time = response_time;
+
+  return result;
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/stream_model_update_request.h b/chromium/components/feed/core/v2/stream_model_update_request.h
new file mode 100644
index 00000000000..6aea209a782
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model_update_request.h
@@ -0,0 +1,74 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_STREAM_MODEL_UPDATE_REQUEST_H_
+#define COMPONENTS_FEED_CORE_V2_STREAM_MODEL_UPDATE_REQUEST_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/proto/v2/wire/data_operation.pb.h"
+#include "components/feed/core/proto/v2/wire/response.pb.h"
+
+namespace feed {
+
+// Data for updating StreamModel. This can be sourced from the network or
+// persistent storage.
+struct StreamModelUpdateRequest {
+ public:
+  enum class Source {
+    kNetworkUpdate,
+    kInitialLoadFromStore,
+  };
+
+  StreamModelUpdateRequest();
+  ~StreamModelUpdateRequest();
+  StreamModelUpdateRequest(const StreamModelUpdateRequest&);
+  StreamModelUpdateRequest& operator=(const StreamModelUpdateRequest&);
+
+  // Whether this data originates is from the initial load of content from
+  // the local data store.
+  Source source = Source::kNetworkUpdate;
+
+  // The set of Contents marked UPDATE_OR_APPEND in the response, in the order
+  // in which they were received.
+  std::vector<feedstore::Content> content;
+
+  // Contains the root ContentId, tokens, a timestamp for when the most recent
+  // content was added, and a list of ContentIds for clusters in the response.
+  feedstore::StreamData stream_data;
+
+  // The set of StreamSharedStates marked UPDATE_OR_APPEND in the order in which
+  // they were received.
+  std::vector<feedstore::StreamSharedState> shared_states;
+
+  std::vector<feedstore::StreamStructure> stream_structures;
+
+  // If this data originates from the network, this is the server-reported time
+  // at which the request was fulfilled.
+  // TODO(harringtond): Use this or remove it.
+  int64_t server_response_time = 0;
+
+  // If this data originates from the network, this is the time taken by the
+  // server to produce the response.
+  // TODO(harringtond): Use this or remove it.
+  base::TimeDelta response_time;
+
+  int32_t max_structure_sequence_number = 0;
+};
+
+base::Optional<feedstore::DataOperation> TranslateDataOperation(
+    feedwire::DataOperation wire_operation);
+
+std::unique_ptr<StreamModelUpdateRequest> TranslateWireResponse(
+    feedwire::Response response,
+    base::TimeDelta response_time,
+    base::Time current_time);
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_STREAM_MODEL_UPDATE_REQUEST_H_
diff --git a/chromium/components/feed/core/v2/stream_model_update_request_unittest.cc b/chromium/components/feed/core/v2/stream_model_update_request_unittest.cc
new file mode 100644
index 00000000000..1e70748d99a
--- /dev/null
+++ b/chromium/components/feed/core/v2/stream_model_update_request_unittest.cc
@@ -0,0 +1,146 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/stream_model_update_request.h"
+
+#include <string>
+
+#include "base/base_paths.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/path_service.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/time/time.h"
+#include "components/feed/core/proto/v2/wire/feed_response.pb.h"
+#include "components/feed/core/proto/v2/wire/response.pb.h"
+#include "components/feed/core/v2/proto_util.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace feed {
+namespace {
+
+const char kResponsePbPath[] = "components/test/data/feed/response.binarypb";
+constexpr base::TimeDelta kResponseTime = base::TimeDelta::FromSeconds(42);
+const base::Time kCurrentTime =
+    base::Time::UnixEpoch() + base::TimeDelta::FromDays(123);
+// TODO(iwells): Replace response.binarypb with a response that uses the new
+// wire protocol.
+//
+// Since we're currently using a Jardin response which includes a
+// Piet shared state, and translation skips handling Piet shared states, we
+// expect to have only 33 StreamStructures even though there are 34 wire
+// operations.
+const int kExpectedStreamStructureCount = 33;
+const size_t kExpectedContentCount = 10;
+const size_t kExpectedSharedStateCount = 0;
+
+std::string ContentIdToString(const feedwire::ContentId& content_id) {
+  return "{content_domain: \"" + content_id.content_domain() +
+         "\", id: " + base::NumberToString(content_id.id()) + ", type: \"" +
+         feedwire::ContentId::Type_Name(content_id.type()) + "\"}";
+}
+
+feedwire::Response TestWireResponse() {
+  // Read and parse response.binarypb.
+  base::FilePath response_file_path;
+  CHECK(base::PathService::Get(base::DIR_SOURCE_ROOT, &response_file_path));
+  response_file_path = response_file_path.AppendASCII(kResponsePbPath);
+
+  CHECK(base::PathExists(response_file_path));
+
+  std::string response_data;
+  CHECK(base::ReadFileToString(response_file_path, &response_data));
+
+  feedwire::Response response;
+  CHECK(response.ParseFromString(response_data));
+  return response;
+}
+
+}  // namespace
+
+// TODO(iwells): Test failure cases once the new protos are ready.
+
+TEST(StreamModelUpdateRequestTest, TranslateRealResponse) {
+  // Tests how proto translation works on a real response from the server.
+  //
+  // The response will periodically need to be updated as changes are made to
+  // the server. Update testdata/response.textproto and then run
+  // tools/generate_test_response_binarypb.sh.
+
+  feedwire::Response response = TestWireResponse();
+  feedwire::FeedResponse feed_response = response.feed_response();
+
+  // TODO(iwells): Make these exactly equal once we aren't using an old
+  // response.
+  ASSERT_EQ(feed_response.data_operation_size(),
+            kExpectedStreamStructureCount + 1);
+
+  std::unique_ptr<StreamModelUpdateRequest> translated =
+      TranslateWireResponse(response, kResponseTime, kCurrentTime);
+
+  ASSERT_TRUE(translated);
+  EXPECT_EQ(kCurrentTime, feedstore::GetLastAddedTime(translated->stream_data));
+  ASSERT_EQ(translated->stream_structures.size(),
+            static_cast<size_t>(kExpectedStreamStructureCount));
+
+  const std::vector<feedstore::StreamStructure>& structures =
+      translated->stream_structures;
+
+  // Check CLEAR_ALL:
+  EXPECT_EQ(structures[0].operation(), feedstore::StreamStructure::CLEAR_ALL);
+
+  // TODO(iwells): Check the shared state once we have a new
+
+  // Check UPDATE_OR_APPEND for the root:
+  EXPECT_EQ(structures[1].operation(),
+            feedstore::StreamStructure::UPDATE_OR_APPEND);
+  EXPECT_EQ(structures[1].type(), feedstore::StreamStructure::STREAM);
+  EXPECT_TRUE(structures[1].has_content_id());
+  EXPECT_FALSE(structures[1].has_parent_id());
+
+  feedwire::ContentId root_content_id = structures[1].content_id();
+
+  // Content:
+  EXPECT_EQ(structures[2].operation(),
+            feedstore::StreamStructure::UPDATE_OR_APPEND);
+  EXPECT_EQ(structures[2].type(), feedstore::StreamStructure::CONTENT);
+  EXPECT_TRUE(structures[2].has_content_id());
+  EXPECT_TRUE(structures[2].has_parent_id());
+
+  // TODO(iwells): Uncomment when these are available.
+  // EXPECT_TRUE(structures[3].has_content_info());
+  // EXPECT_NE(structures[3].content_info().score(), 0.);
+  // EXPECT_NE(structures[3].content_info().availability_time_seconds(), 0);
+  // EXPECT_TRUE(structures[3].content_info().has_representation_data());
+  // EXPECT_TRUE(structures[3].content_info().has_offline_metadata());
+
+  ASSERT_GT(translated->content.size(), 0UL);
+  EXPECT_EQ(ContentIdToString(translated->content[0].content_id()),
+            ContentIdToString(structures[2].content_id()));
+  // TODO(iwells): Check content.frame() once this is available.
+
+  // Non-content structures:
+  EXPECT_EQ(structures[3].operation(),
+            feedstore::StreamStructure::UPDATE_OR_APPEND);
+  // TODO(iwells): This is a CARD. Remove once we have a new response.
+  EXPECT_EQ(structures[3].type(), feedstore::StreamStructure::UNKNOWN_TYPE);
+  EXPECT_TRUE(structures[3].has_content_id());
+  EXPECT_TRUE(structures[3].has_parent_id());
+
+  EXPECT_EQ(structures[4].operation(),
+            feedstore::StreamStructure::UPDATE_OR_APPEND);
+  EXPECT_EQ(structures[4].type(), feedstore::StreamStructure::CLUSTER);
+  EXPECT_TRUE(structures[4].has_content_id());
+  EXPECT_TRUE(structures[4].has_parent_id());
+  EXPECT_EQ(ContentIdToString(structures[4].parent_id()),
+            ContentIdToString(root_content_id));
+
+  // The other members:
+  EXPECT_EQ(translated->content.size(), kExpectedContentCount);
+  EXPECT_EQ(translated->shared_states.size(), kExpectedSharedStateCount);
+
+  EXPECT_EQ(translated->response_time, kResponseTime);
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/tasks/load_stream_from_store_task.cc b/chromium/components/feed/core/v2/tasks/load_stream_from_store_task.cc
new file mode 100644
index 00000000000..c3c2a261a31
--- /dev/null
+++ b/chromium/components/feed/core/v2/tasks/load_stream_from_store_task.cc
@@ -0,0 +1,127 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/tasks/load_stream_from_store_task.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "base/time/clock.h"
+#include "components/feed/core/proto/v2/store.pb.h"
+#include "components/feed/core/v2/feed_store.h"
+#include "components/feed/core/v2/proto_util.h"
+#include "components/feed/core/v2/public/feed_stream_api.h"
+#include "components/feed/core/v2/scheduling.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+
+namespace feed {
+
+LoadStreamFromStoreTask::Result::Result() = default;
+LoadStreamFromStoreTask::Result::~Result() = default;
+LoadStreamFromStoreTask::Result::Result(Result&&) = default;
+LoadStreamFromStoreTask::Result& LoadStreamFromStoreTask::Result::operator=(
+    Result&&) = default;
+
+LoadStreamFromStoreTask::LoadStreamFromStoreTask(
+    FeedStore* store,
+    const base::Clock* clock,
+    UserClass user_class,
+    base::OnceCallback<void(Result)> callback)
+    : store_(store),
+      clock_(clock),
+      user_class_(user_class),
+      result_callback_(std::move(callback)),
+      update_request_(std::make_unique<StreamModelUpdateRequest>()) {}
+
+LoadStreamFromStoreTask::~LoadStreamFromStoreTask() = default;
+
+void LoadStreamFromStoreTask::Run() {
+  store_->LoadStream(
+      base::BindOnce(&LoadStreamFromStoreTask::LoadStreamDone, GetWeakPtr()));
+}
+
+void LoadStreamFromStoreTask::LoadStreamDone(
+    FeedStore::LoadStreamResult result) {
+  if (result.read_error) {
+    Complete(LoadStreamStatus::kFailedWithStoreError);
+    return;
+  }
+  if (result.stream_structures.empty()) {
+    Complete(LoadStreamStatus::kNoStreamDataInStore);
+    return;
+  }
+  if (!ignore_staleness_) {
+    const base::TimeDelta content_age =
+        clock_->Now() - feedstore::GetLastAddedTime(result.stream_data);
+    if (content_age < base::TimeDelta()) {
+      Complete(LoadStreamStatus::kDataInStoreIsStaleTimestampInFuture);
+      return;
+    } else if (ShouldWaitForNewContent(user_class_, true, content_age)) {
+      Complete(LoadStreamStatus::kDataInStoreIsStale);
+      return;
+    }
+  }
+
+  // TODO(harringtond): Add other failure cases?
+
+  std::vector<ContentId> referenced_content_ids;
+  for (const feedstore::StreamStructureSet& structure_set :
+       result.stream_structures) {
+    for (const feedstore::StreamStructure& structure :
+         structure_set.structures()) {
+      if (structure.type() == feedstore::StreamStructure::CONTENT) {
+        referenced_content_ids.push_back(structure.content_id());
+      }
+    }
+  }
+
+  store_->ReadContent(
+      std::move(referenced_content_ids), {result.stream_data.shared_state_id()},
+      base::BindOnce(&LoadStreamFromStoreTask::LoadContentDone, GetWeakPtr()));
+
+  update_request_->stream_data = std::move(result.stream_data);
+
+  // Move stream structures into the update request.
+  // These need sorted by sequence number, and then inserted into
+  // |update_request_->stream_structures|.
+  std::sort(result.stream_structures.begin(), result.stream_structures.end(),
+            [](const feedstore::StreamStructureSet& a,
+               const feedstore::StreamStructureSet& b) {
+              return a.sequence_number() < b.sequence_number();
+            });
+
+  for (feedstore::StreamStructureSet& structure_set :
+       result.stream_structures) {
+    update_request_->max_structure_sequence_number =
+        structure_set.sequence_number();
+    for (feedstore::StreamStructure& structure :
+         *structure_set.mutable_structures()) {
+      update_request_->stream_structures.push_back(std::move(structure));
+    }
+  }
+}
+
+void LoadStreamFromStoreTask::LoadContentDone(
+    std::vector<feedstore::Content> content,
+    std::vector<feedstore::StreamSharedState> shared_states) {
+  update_request_->content = std::move(content);
+  update_request_->shared_states = std::move(shared_states);
+
+  update_request_->source =
+      StreamModelUpdateRequest::Source::kInitialLoadFromStore;
+
+  Complete(LoadStreamStatus::kLoadedFromStore);
+}
+
+void LoadStreamFromStoreTask::Complete(LoadStreamStatus status) {
+  Result task_result;
+  task_result.status = status;
+  if (status == LoadStreamStatus::kLoadedFromStore) {
+    task_result.update_request = std::move(update_request_);
+  }
+  std::move(result_callback_).Run(std::move(task_result));
+  TaskComplete();
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/tasks/load_stream_from_store_task.h b/chromium/components/feed/core/v2/tasks/load_stream_from_store_task.h
new file mode 100644
index 00000000000..3718c2c9fd1
--- /dev/null
+++ b/chromium/components/feed/core/v2/tasks/load_stream_from_store_task.h
@@ -0,0 +1,71 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_TASKS_LOAD_STREAM_FROM_STORE_TASK_H_
+#define COMPONENTS_FEED_CORE_V2_TASKS_LOAD_STREAM_FROM_STORE_TASK_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "components/feed/core/v2/enums.h"
+#include "components/feed/core/v2/feed_store.h"
+#include "components/offline_pages/task/task.h"
+
+namespace base {
+class Clock;
+}
+
+namespace feed {
+struct StreamModelUpdateRequest;
+
+// Attempts to load stream data from persistent storage.
+class LoadStreamFromStoreTask : public offline_pages::Task {
+ public:
+  struct Result {
+    Result();
+    ~Result();
+    Result(Result&&);
+    Result& operator=(Result&&);
+    LoadStreamStatus status = LoadStreamStatus::kNoStatus;
+    std::unique_ptr<StreamModelUpdateRequest> update_request;
+  };
+
+  LoadStreamFromStoreTask(FeedStore* store,
+                          const base::Clock* clock,
+                          UserClass user_class,
+                          base::OnceCallback<void(Result)> callback);
+  ~LoadStreamFromStoreTask() override;
+  LoadStreamFromStoreTask(const LoadStreamFromStoreTask&) = delete;
+  LoadStreamFromStoreTask& operator=(const LoadStreamFromStoreTask&) = delete;
+
+  void IgnoreStalenessForTesting() { ignore_staleness_ = true; }
+
+ private:
+  void Run() override;
+
+  void LoadStreamDone(FeedStore::LoadStreamResult);
+  void LoadContentDone(std::vector<feedstore::Content> content,
+                       std::vector<feedstore::StreamSharedState> shared_states);
+  void Complete(LoadStreamStatus status);
+
+  base::WeakPtr<LoadStreamFromStoreTask> GetWeakPtr() {
+    return weak_ptr_factory_.GetWeakPtr();
+  }
+
+  FeedStore* store_;  // Unowned.
+  const base::Clock* clock_;
+  UserClass user_class_;
+  bool ignore_staleness_ = false;
+  base::OnceCallback<void(Result)> result_callback_;
+
+  std::unique_ptr<StreamModelUpdateRequest> update_request_;
+
+  base::WeakPtrFactory<LoadStreamFromStoreTask> weak_ptr_factory_{this};
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_TASKS_LOAD_STREAM_FROM_STORE_TASK_H_
diff --git a/chromium/components/feed/core/v2/tasks/load_stream_task.cc b/chromium/components/feed/core/v2/tasks/load_stream_task.cc
new file mode 100644
index 00000000000..82e10860897
--- /dev/null
+++ b/chromium/components/feed/core/v2/tasks/load_stream_task.cc
@@ -0,0 +1,120 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/tasks/load_stream_task.h"
+
+#include <memory>
+#include <utility>
+
+#include "base/bind_helpers.h"
+#include "base/logging.h"
+#include "base/time/clock.h"
+#include "base/time/time.h"
+#include "components/feed/core/proto/v2/wire/client_info.pb.h"
+#include "components/feed/core/proto/v2/wire/feed_request.pb.h"
+#include "components/feed/core/proto/v2/wire/request.pb.h"
+#include "components/feed/core/v2/feed_network.h"
+#include "components/feed/core/v2/feed_stream.h"
+#include "components/feed/core/v2/stream_model.h"
+#include "components/feed/core/v2/stream_model_update_request.h"
+
+namespace feed {
+
+LoadStreamTask::LoadStreamTask(FeedStream* stream,
+                               base::OnceCallback<void(Result)> done_callback)
+    : stream_(stream), done_callback_(std::move(done_callback)) {}
+
+LoadStreamTask::~LoadStreamTask() = default;
+
+void LoadStreamTask::Run() {
+  // Phase 1.
+  //  - Return early if the model is already loaded.
+  //  - Try to load from persistent storage.
+
+  // Don't load if the model is already loaded.
+  if (stream_->GetModel()) {
+    Done(LoadStreamStatus::kModelAlreadyLoaded);
+    return;
+  }
+
+  load_from_store_task_ = std::make_unique<LoadStreamFromStoreTask>(
+      stream_->GetStore(), stream_->GetClock(), stream_->GetUserClass(),
+      base::BindOnce(&LoadStreamTask::LoadFromStoreComplete, GetWeakPtr()));
+  load_from_store_task_->Execute(base::DoNothing());
+}
+
+void LoadStreamTask::LoadFromStoreComplete(
+    LoadStreamFromStoreTask::Result result) {
+  load_from_store_status_ = result.status;
+  // Phase 2.
+  //  - If loading from store works, update the model.
+  //  - Otherwise, try to load from the network.
+
+  if (result.status == LoadStreamStatus::kLoadedFromStore) {
+    auto model = std::make_unique<StreamModel>();
+    model->Update(std::move(result.update_request));
+    stream_->LoadModel(std::move(model));
+    Done(LoadStreamStatus::kLoadedFromStore);
+    return;
+  }
+
+  LoadStreamStatus final_status = stream_->ShouldMakeFeedQueryRequest();
+  if (final_status != LoadStreamStatus::kNoStatus) {
+    Done(final_status);
+    return;
+  }
+
+  // TODO(harringtond): Add throttling.
+  // TODO(harringtond): Request parameters here are all placeholder values.
+  feedwire::Request request;
+  feedwire::ClientInfo& client_info =
+      *request.mutable_feed_request()->mutable_client_info();
+  client_info.set_platform_type(feedwire::ClientInfo::ANDROID_ID);
+  client_info.set_app_type(feedwire::ClientInfo::CHROME);
+  request.mutable_feed_request()->mutable_feed_query()->set_reason(
+      feedwire::FeedQuery::MANUAL_REFRESH);
+
+  fetch_start_time_ = base::TimeTicks::Now();
+  stream_->GetNetwork()->SendQueryRequest(
+      request,
+      base::BindOnce(&LoadStreamTask::QueryRequestComplete, GetWeakPtr()));
+}
+
+void LoadStreamTask::QueryRequestComplete(
+    FeedNetwork::QueryRequestResult result) {
+  DCHECK(!stream_->GetModel());
+  if (!result.response_body) {
+    Done(LoadStreamStatus::kNoResponseBody);
+    return;
+  }
+
+  std::unique_ptr<StreamModelUpdateRequest> update_request =
+      stream_->GetWireResponseTranslator()->TranslateWireResponse(
+          *result.response_body, base::TimeTicks::Now() - fetch_start_time_,
+          stream_->GetClock()->Now());
+  if (!update_request) {
+    Done(LoadStreamStatus::kProtoTranslationFailed);
+    return;
+  }
+
+  stream_->GetStore()->SaveFullStream(
+      std::make_unique<StreamModelUpdateRequest>(*update_request),
+      base::DoNothing());
+
+  auto model = std::make_unique<StreamModel>();
+  model->Update(std::move(update_request));
+  stream_->LoadModel(std::move(model));
+
+  Done(LoadStreamStatus::kLoadedFromNetwork);
+}
+
+void LoadStreamTask::Done(LoadStreamStatus status) {
+  Result result;
+  result.load_from_store_status = load_from_store_status_;
+  result.final_status = status;
+  std::move(done_callback_).Run(result);
+  TaskComplete();
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/tasks/load_stream_task.h b/chromium/components/feed/core/v2/tasks/load_stream_task.h
new file mode 100644
index 00000000000..ad19cd90d64
--- /dev/null
+++ b/chromium/components/feed/core/v2/tasks/load_stream_task.h
@@ -0,0 +1,62 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_TASKS_LOAD_STREAM_TASK_H_
+#define COMPONENTS_FEED_CORE_V2_TASKS_LOAD_STREAM_TASK_H_
+
+#include <memory>
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+#include "components/feed/core/v2/enums.h"
+#include "components/feed/core/v2/feed_network.h"
+#include "components/feed/core/v2/tasks/load_stream_from_store_task.h"
+#include "components/offline_pages/task/task.h"
+
+namespace feed {
+class FeedStream;
+
+// Loads the stream model from storage or network.
+// If successful, this directly forces a model load in |FeedStream()|
+// before completing the task.
+// TODO(harringtond): If we read data from the network, it needs to be
+// persisted.
+class LoadStreamTask : public offline_pages::Task {
+ public:
+  struct Result {
+    Result() = default;
+    explicit Result(LoadStreamStatus a_final_status)
+        : final_status(a_final_status) {}
+    // Final status of loading the stream.
+    LoadStreamStatus final_status = LoadStreamStatus::kNoStatus;
+    // Status of just loading the stream from the persistent store, if that
+    // was attempted.
+    LoadStreamStatus load_from_store_status = LoadStreamStatus::kNoStatus;
+  };
+  explicit LoadStreamTask(FeedStream* stream,
+                          base::OnceCallback<void(Result)> done_callback);
+  ~LoadStreamTask() override;
+  LoadStreamTask(const LoadStreamTask&) = delete;
+  LoadStreamTask& operator=(const LoadStreamTask&) = delete;
+
+ private:
+  void Run() override;
+  base::WeakPtr<LoadStreamTask> GetWeakPtr() {
+    return weak_ptr_factory_.GetWeakPtr();
+  }
+
+  void LoadFromStoreComplete(LoadStreamFromStoreTask::Result result);
+  void QueryRequestComplete(FeedNetwork::QueryRequestResult result);
+  void Done(LoadStreamStatus status);
+
+  FeedStream* stream_;  // Unowned.
+  std::unique_ptr<LoadStreamFromStoreTask> load_from_store_task_;
+  LoadStreamStatus load_from_store_status_ = LoadStreamStatus::kNoStatus;
+  base::TimeTicks fetch_start_time_;
+  base::OnceCallback<void(Result)> done_callback_;
+  base::WeakPtrFactory<LoadStreamTask> weak_ptr_factory_{this};
+};
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_TASKS_LOAD_STREAM_TASK_H_
diff --git a/chromium/components/feed/core/v2/tasks/wait_for_store_initialize_task.cc b/chromium/components/feed/core/v2/tasks/wait_for_store_initialize_task.cc
new file mode 100644
index 00000000000..27f73cbb1be
--- /dev/null
+++ b/chromium/components/feed/core/v2/tasks/wait_for_store_initialize_task.cc
@@ -0,0 +1,21 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/feed/core/v2/tasks/wait_for_store_initialize_task.h"
+
+#include "components/feed/core/v2/feed_store.h"
+
+namespace feed {
+
+WaitForStoreInitializeTask::WaitForStoreInitializeTask(FeedStore* store)
+    : store_(store) {}
+WaitForStoreInitializeTask::~WaitForStoreInitializeTask() = default;
+
+void WaitForStoreInitializeTask::Run() {
+  // |this| stays alive as long as the |store_|, so Unretained is safe.
+  store_->Initialize(base::BindOnce(&WaitForStoreInitializeTask::TaskComplete,
+                                    base::Unretained(this)));
+}
+
+}  // namespace feed
diff --git a/chromium/components/feed/core/v2/tasks/wait_for_store_initialize_task.h b/chromium/components/feed/core/v2/tasks/wait_for_store_initialize_task.h
new file mode 100644
index 00000000000..f7640676c68
--- /dev/null
+++ b/chromium/components/feed/core/v2/tasks/wait_for_store_initialize_task.h
@@ -0,0 +1,31 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_FEED_CORE_V2_TASKS_WAIT_FOR_STORE_INITIALIZE_TASK_H_
+#define COMPONENTS_FEED_CORE_V2_TASKS_WAIT_FOR_STORE_INITIALIZE_TASK_H_
+
+#include "components/offline_pages/task/task.h"
+
+namespace feed {
+class FeedStore;
+
+// Initializes |store|. This task is run first so that other tasks can assume
+// storage is initialized.
+class WaitForStoreInitializeTask : public offline_pages::Task {
+ public:
+  explicit WaitForStoreInitializeTask(FeedStore* store);
+  ~WaitForStoreInitializeTask() override;
+  WaitForStoreInitializeTask(const WaitForStoreInitializeTask&) = delete;
+  WaitForStoreInitializeTask& operator=(const WaitForStoreInitializeTask&) =
+      delete;
+
+ private:
+  void Run() override;
+
+  FeedStore* store_;
+};
+
+}  // namespace feed
+
+#endif  // COMPONENTS_FEED_CORE_V2_TASKS_WAIT_FOR_STORE_INITIALIZE_TASK_H_
diff --git a/chromium/components/feed/core/v2/tools/__init__.py b/chromium/components/feed/core/v2/tools/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/chromium/components/feed/core/v2/tools/__init__.py
diff --git a/chromium/components/feed/core/v2/tools/feed_response_to_textproto.sh b/chromium/components/feed/core/v2/tools/feed_response_to_textproto.sh
new file mode 100755
index 00000000000..48c3da5d410
--- /dev/null
+++ b/chromium/components/feed/core/v2/tools/feed_response_to_textproto.sh
@@ -0,0 +1,25 @@
+#!/bin/bash
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+#
+# Converts a Feed HTTP response from binary to text using proto definitions from
+# Chromium.
+#
+# Usage: feed_response_to_textproto.sh <in.binarypb> <out.textproto>
+
+IN_FILE=$1
+OUT_FILE=$2
+TMP_FILE=/tmp/trimmedfeedresponse.binarypb
+
+CHROMIUM_SRC=$(realpath $(dirname $(readlink -f $0))/../../../../..)
+FEEDPROTO="$CHROMIUM_SRC/components/feed/core/proto"
+
+# Responses start with a 4-byte length value that must be removed.
+tail -c +4 $IN_FILE > $TMP_FILE
+
+python3 $CHROMIUM_SRC/components/feed/core/v2/tools/textpb_to_binarypb.py \
+  --chromium_path=$CHROMIUM_SRC \
+  --output_file=$OUT_FILE \
+  --source_file=$TMP_FILE \
+  --direction=reverse
diff --git a/chromium/components/feed/core/v2/tools/generate_test_response_binarypb.sh b/chromium/components/feed/core/v2/tools/generate_test_response_binarypb.sh
new file mode 100755
index 00000000000..8265181451c
--- /dev/null
+++ b/chromium/components/feed/core/v2/tools/generate_test_response_binarypb.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+CHROMIUM_SRC=$(realpath $(dirname $(readlink -f $0))/../../../../..)
+OUT_DIR=$CHROMIUM_SRC/components/test/data/feed
+
+if [ ! -d $OUT_DIR ]; then
+  echo "Output directory $OUT_DIR doesn't exist."
+  exit 1
+fi
+
+python3 $CHROMIUM_SRC/components/feed/core/v2/tools/textpb_to_binarypb.py \
+  --chromium_path=$CHROMIUM_SRC \
+  --output_file=$OUT_DIR/response.binarypb \
+  --source_file=\
+$CHROMIUM_SRC/components/feed/core/v2/testdata/response.textproto
diff --git a/chromium/components/feed/core/v2/tools/protoc_util.py b/chromium/components/feed/core/v2/tools/protoc_util.py
new file mode 100755
index 00000000000..41104fe5db5
--- /dev/null
+++ b/chromium/components/feed/core/v2/tools/protoc_util.py
@@ -0,0 +1,63 @@
+#!/usr/bin/python3
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Lint as: python3
+"""The tools provides lot of protoc related helper functions."""
+
+import glob
+import os
+import subprocess
+
+_protoc_path = None
+
+def run_command(args, input):
+  """Uses subprocess to execute the command line args."""
+  proc = subprocess.run(
+      args,
+      input=input,
+      stdout=subprocess.PIPE,
+      stderr=subprocess.PIPE,
+      check=True)
+  return proc.stdout
+
+
+def get_protoc_common_args(root_dir, proto_path):
+  """Returns a list of protoc common args as a list."""
+  result = [
+      '-I' + os.path.join(root_dir)
+  ]
+  for root, _, files in os.walk(os.path.join(root_dir, proto_path)):
+    result += [os.path.join(root, f) for f in files if f.endswith('.proto')]
+
+  return result
+
+
+def encode_proto(text, message_name, root_dir, proto_path):
+  """Calls a command line to encode the text string and returns binary bytes."""
+  return run_command([protoc_path(root_dir), '--encode=' + message_name]
+                     + get_protoc_common_args(root_dir, proto_path),
+                     text.encode())
+
+
+def decode_proto(data, message_name, root_dir, proto_path):
+  """Calls a command line to decode the binary bytes array into text string."""
+  return run_command([protoc_path(root_dir), '--decode=' + message_name
+                     ] + get_protoc_common_args(root_dir, proto_path),
+                     data).decode('utf-8')
+
+
+def protoc_path(root_dir):
+  """Returns the path to the proto compiler, protoc."""
+  global _protoc_path
+  if not _protoc_path:
+    protoc_list = list(
+        glob.glob(os.path.join(root_dir, "out") + "/*/protoc")) + list(
+            glob.glob(os.path.join(root_dir, "out") + "/*/*/protoc"))
+    if not len(protoc_list):
+      print("Can't find a suitable build output directory",
+            "(it should have protoc)")
+      sys.exit(1)
+    _protoc_path = protoc_list[0]
+  return _protoc_path
diff --git a/chromium/components/feed/core/v2/tools/textpb_to_binarypb.py b/chromium/components/feed/core/v2/tools/textpb_to_binarypb.py
new file mode 100755
index 00000000000..14cb23e915e
--- /dev/null
+++ b/chromium/components/feed/core/v2/tools/textpb_to_binarypb.py
@@ -0,0 +1,81 @@
+#!/usr/bin/python3
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Lint as: python3
+"""The tool converts a textpb into a binary proto using chromium protoc binary.
+
+Make sure you have absl-py installed via 'python3 -m pip install absl-py'.
+
+Usage example:
+    python3 ./textpb_to_binarypb.py
+    --chromium_path ~/chromium/src
+    --output_file /tmp/binary.pb
+    --source_file /tmp/original.textpb
+"""
+
+import glob
+import os
+import protoc_util
+import subprocess
+
+from absl import app
+from absl import flags
+
+DEFAULT_MESSAGE = 'feedwire.Response'
+
+FLAGS = flags.FLAGS
+FLAGS = flags.FLAGS
+flags.DEFINE_string('chromium_path', '', 'The path of your chromium depot.')
+flags.DEFINE_string('output_file', '', 'The target output binary file path.')
+flags.DEFINE_string('source_file', '',
+                    'The source proto file, in textpb format, path.')
+flags.DEFINE_string('message',
+                    DEFAULT_MESSAGE,
+                    'The message to look for in source_file.')
+flags.DEFINE_string('direction', 'forward',
+                    'Set --direction=reverse to convert binary to text.')
+
+COMPONENT_FEED_PROTO_PATH = 'components/feed/core/proto'
+
+def text_to_binary():
+  with open(FLAGS.source_file, mode='r') as file:
+    value_text_proto = file.read()
+
+  encoded = protoc_util.encode_proto(value_text_proto, FLAGS.message,
+                                     FLAGS.chromium_path,
+                                     COMPONENT_FEED_PROTO_PATH)
+  with open(FLAGS.output_file, mode='wb') as file:
+    file.write(encoded)
+
+def binary_to_text():
+  with open(FLAGS.source_file, mode='rb') as file:
+    value_text_proto = file.read()
+
+  encoded = protoc_util.decode_proto(value_text_proto, FLAGS.message,
+                                     FLAGS.chromium_path,
+                                     COMPONENT_FEED_PROTO_PATH)
+
+  with open(FLAGS.output_file, mode='w') as file:
+    file.write(encoded)
+
+def main(argv):
+  if len(argv) > 1:
+    raise app.UsageError('Too many command-line arguments.')
+  if not FLAGS.chromium_path:
+    raise app.UsageError('chromium_path flag must be set.')
+  if not FLAGS.source_file:
+    raise app.UsageError('source_file flag must be set.')
+  if not FLAGS.output_file:
+    raise app.UsageError('output_file flag must be set.')
+  if FLAGS.direction != 'forward' and FLAGS.direction != 'reverse':
+    raise app.UsageError('direction must be forward or reverse')
+
+  if FLAGS.direction == 'forward':
+    text_to_binary()
+  elif FLAGS.direction == 'reverse':
+    binary_to_text()
+
+if __name__ == '__main__':
+  app.run(main)
diff --git a/chromium/components/feed/feed_feature_list.cc b/chromium/components/feed/feed_feature_list.cc
index 25e149321be..b8f44049912 100644
--- a/chromium/components/feed/feed_feature_list.cc
+++ b/chromium/components/feed/feed_feature_list.cc
@@ -24,4 +24,10 @@ const base::FeatureParam<bool> kOnlySetLastRefreshAttemptOnSuccess{
 const base::Feature kInterestFeedNotifications{
     "InterestFeedNotifications", base::FEATURE_DISABLED_BY_DEFAULT};
 
+const base::Feature kInterestFeedFeedback{"InterestFeedFeedback",
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
+
+const base::Feature kReportFeedUserActions{"ReportFeedUserActions",
+                                           base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace feed
diff --git a/chromium/components/feed/feed_feature_list.h b/chromium/components/feed/feed_feature_list.h
index 41342be8e74..fe5e1141bbf 100644
--- a/chromium/components/feed/feed_feature_list.h
+++ b/chromium/components/feed/feed_feature_list.h
@@ -22,6 +22,12 @@ extern const base::FeatureParam<bool> kOnlySetLastRefreshAttemptOnSuccess;
 
 extern const base::Feature kInterestFeedNotifications;
 
+extern const base::Feature kInterestFeedFeedback;
+
+// Indicates if user card clicks and views in Chrome's feed should be reported
+// for personalization.
+extern const base::Feature kReportFeedUserActions;
+
 }  // namespace feed
 
 #endif  // COMPONENTS_FEED_FEED_FEATURE_LIST_H_
diff --git a/chromium/components/feed/tools/__init__.py b/chromium/components/feed/tools/__init__.py
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/chromium/components/feed/tools/__init__.py
diff --git a/chromium/components/feed/tools/content_dump.py b/chromium/components/feed/tools/content_dump.py
index 0f28a9ef481..91d5cdee017 100755
--- a/chromium/components/feed/tools/content_dump.py
+++ b/chromium/components/feed/tools/content_dump.py
@@ -14,15 +14,16 @@
 # Make any desired modifications, and then upload the dump back to the connected
 # device.
 # > content_dump.py --device=FA77D0303076 --apk='com.chrome.canary' --reverse
+import argparse
+import glob
 import os
+import plyvel
+import protoc_util
 import re
-import sys
-import argparse
 import subprocess
-import glob
-from os.path import join, dirname, realpath
+import sys
 
-import plyvel
+from os.path import join, dirname, realpath
 
 # A dynamic import for encoding and decoding of escaped textproto strings.
 _prototext_mod = None
@@ -61,21 +62,8 @@ DUMP_DIR = args.dump_to
 DB_PATH = args.db
 CONTENT_DB_PATH = join(DB_PATH, 'content')
 DEVICE_DB_PATH = "/data/data/{}/app_chrome/Default/feed".format(args.apk)
-_protoc_path = None
-
-
-# Returns the path to the proto compiler, protoc.
-def protoc_path():
-  global _protoc_path
-  if not _protoc_path:
-    protoc_list = list(glob.glob(join(ROOT_DIR, "out") + "/*/protoc")) + list(
-        glob.glob(join(ROOT_DIR, "out") + "/*/*/protoc"))
-    if not len(protoc_list):
-      print("Can't find a suitable build output directory",
-            "(it should have protoc)")
-      sys.exit(1)
-    _protoc_path = protoc_list[0]
-  return _protoc_path
+CONTENT_STORAGE_PROTO = (
+    'components/feed_library/core/proto/content_storage.proto')
 
 
 def adb_base_args():
@@ -97,45 +85,6 @@ def adb_push_db():
                         ["push", CONTENT_DB_PATH, DEVICE_DB_PATH])
 
 
-def get_feed_protos():
-  result = [
-      join(ROOT_DIR, 'components/feed_library/core/proto/content_storage.proto')
-  ]
-  for root, _, files in os.walk(join(ROOT_DIR, "third_party/feed_library")):
-    result += [join(root, f) for f in files if f.endswith('.proto')]
-
-  return result
-
-
-protoc_common_args = [
-    '-I' + join(ROOT_DIR, 'third_party/feed_library/src'), '-I' + join(ROOT_DIR)
-] + get_feed_protos()
-
-
-def run_command(args, input):
-  proc = subprocess.run(
-      args,
-      input=input,
-      stdout=subprocess.PIPE,
-      stderr=subprocess.PIPE,
-      check=True)
-  return proc.stdout
-
-
-# Decode a binary proto into textproto format.
-def decode_proto(data, message_name):
-  return run_command(
-      [protoc_path(), '--decode=' + message_name] + protoc_common_args,
-      data).decode('utf-8')
-
-
-# Encode a textproto into binary proto format.
-def encode_proto(text, message_name):
-  return run_command(
-      [protoc_path(), '--encode=' + message_name] + protoc_common_args,
-      text.encode())
-
-
 # Ignore DB entries with the 'sp::' prefix, as they are not yet supported.
 def is_key_supported(key):
   return not key.startswith('sp::')
@@ -155,13 +104,15 @@ def proto_message_from_db_key(key):
 def extract_db_entry(key, data):
   # DB entries are feed.ContentStorageProto messages. First extract
   # the content_data contained within.
-  text_proto = decode_proto(data, 'feed.ContentStorageProto')
+  text_proto = protoc_util.decode_proto(data, 'feed.ContentStorageProto',
+                                        ROOT_DIR, CONTENT_STORAGE_PROTO)
   m = re.search(r"content_data: \"((?:\\\"|[^\"])*)\"", text_proto)
   raw_data = prototext().CUnescape(m.group(1))
 
   # Next, convert raw_data into a textproto. The DB key informs which message
   # is stored.
-  result = decode_proto(raw_data, proto_message_from_db_key(key))
+  result = protoc_util.decode_proto(raw_data, proto_message_from_db_key(key),
+                                    ROOT_DIR, CONTENT_STORAGE_PROTO)
   return result
 
 
@@ -196,15 +147,17 @@ def load():
         key = file.read().strip()
       with open(join(DUMP_DIR, f), 'r') as file:
         value_text_proto = file.read()
-      value_encoded = encode_proto(value_text_proto,
-                                   proto_message_from_db_key(key))
+      value_encoded = protoc_util.encode_proto(value_text_proto,
+                                               proto_message_from_db_key(key),
+                                               ROOT_DIR, CONTENT_STORAGE_PROTO)
       # Create binary feed.ContentStorageProto by encoding its textproto.
       content_storage_text = 'key: "{}"\ncontent_data: "{}"'.format(
           prototext().CEscape(key, False),
           prototext().CEscape(value_encoded, False))
 
-      store_encoded = encode_proto(content_storage_text,
-                                   'feed.ContentStorageProto')
+      store_encoded = protoc_util.encode_proto(content_storage_text,
+                                               'feed.ContentStorageProto',
+                                               ROOT_DIR, CONTENT_STORAGE_PROTO)
       db.put(key.encode(), store_encoded)
   db.close()
   adb_push_db()
diff --git a/chromium/components/feed/tools/mockserver_textpb_to_binary.py b/chromium/components/feed/tools/mockserver_textpb_to_binary.py
new file mode 100755
index 00000000000..b6d75745b27
--- /dev/null
+++ b/chromium/components/feed/tools/mockserver_textpb_to_binary.py
@@ -0,0 +1,64 @@
+#!/usr/bin/python3
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Lint as: python3
+"""The tool converts a textpb into a binary proto using chromium protoc binary.
+
+After converting a feed response textpb file into a mockserver textpb file using
+the proto_convertor script, then a engineer runs this script to encode the
+mockserver textpb file into a binary proto file that is being used by the feed
+card render test (Refers to go/create-a-feed-card-render-test for more).
+
+Make sure you have absl-py installed via 'python3 -m pip install absl-py'.
+
+Usage example:
+    python3 ./mockserver_textpb_to_binary.py
+    --chromium_path ~/chromium/src
+    --output_file /tmp/binary.pb
+    --source_file /tmp/original.textpb
+    --alsologtostderr
+"""
+
+import glob
+import os
+import protoc_util
+import subprocess
+
+from absl import app
+from absl import flags
+
+FLAGS = flags.FLAGS
+FLAGS = flags.FLAGS
+flags.DEFINE_string('chromium_path', '', 'The path of your chromium depot.')
+flags.DEFINE_string('output_file', '', 'The target output binary file path.')
+flags.DEFINE_string('source_file', '',
+                    'The source proto file, in textpb format, path.')
+
+ENCODE_NAMESPACE = 'components.feed.core.proto.wire.mockserver.MockServer'
+COMPONENT_FEED_PROTO_PATH = 'components/feed/core/proto'
+
+
+def main(argv):
+  if len(argv) > 1:
+    raise app.UsageError('Too many command-line arguments.')
+  if not FLAGS.chromium_path:
+    raise app.UsageError('chromium_path flag must be set.')
+  if not FLAGS.source_file:
+    raise app.UsageError('source_file flag must be set.')
+  if not FLAGS.output_file:
+    raise app.UsageError('output_file flag must be set.')
+
+  with open(FLAGS.source_file) as file:
+    value_text_proto = file.read()
+
+  encoded = protoc_util.encode_proto(value_text_proto, ENCODE_NAMESPACE,
+                                     FLAGS.chromium_path,
+                                     COMPONENT_FEED_PROTO_PATH)
+  with open(FLAGS.output_file, 'wb') as file:
+    file.write(encoded)
+
+
+if __name__ == '__main__':
+  app.run(main)
diff --git a/chromium/components/feed/tools/protoc_util.py b/chromium/components/feed/tools/protoc_util.py
new file mode 100755
index 00000000000..0ff20f2c0b0
--- /dev/null
+++ b/chromium/components/feed/tools/protoc_util.py
@@ -0,0 +1,65 @@
+#!/usr/bin/python3
+# Copyright 2020 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Lint as: python3
+"""The tools provides lot of protoc related helper functions."""
+
+import glob
+import os
+import subprocess
+
+_protoc_path = None
+
+
+def run_command(args, input):
+  """Uses subprocess to execute the command line args."""
+  proc = subprocess.run(
+      args,
+      input=input,
+      stdout=subprocess.PIPE,
+      stderr=subprocess.PIPE,
+      check=True)
+  return proc.stdout
+
+
+def get_protoc_common_args(root_dir, proto_path):
+  """Returns a list of protoc common args as a list."""
+  result = [
+      '-I' + os.path.join(root_dir, 'third_party/feed_library/src'),
+      '-I' + os.path.join(root_dir)
+  ]
+  for root, _, files in os.walk(os.path.join(root_dir, proto_path)):
+    result += [os.path.join(root, f) for f in files if f.endswith('.proto')]
+
+  return result
+
+
+def encode_proto(text, message_name, root_dir, proto_path):
+  """Calls a command line to encode the text string and returns binary bytes."""
+  return run_command([protoc_path(root_dir), '--encode=' + message_name]
+                     + get_protoc_common_args(root_dir, proto_path),
+                     text.encode())
+
+
+def decode_proto(data, message_name, root_dir, proto_path):
+  """Calls a command line to decode the binary bytes array into text string."""
+  return run_command([protoc_path(root_dir), '--decode=' + message_name
+                     ] + get_protoc_common_args(root_dir, proto_path),
+                     data).decode('utf-8')
+
+
+def protoc_path(root_dir):
+  """Returns the path to the proto compiler, protoc."""
+  global _protoc_path
+  if not _protoc_path:
+    protoc_list = list(
+        glob.glob(os.path.join(root_dir, "out") + "/*/protoc")) + list(
+            glob.glob(os.path.join(root_dir, "out") + "/*/*/protoc"))
+    if not len(protoc_list):
+      print("Can't find a suitable build output directory",
+            "(it should have protoc)")
+      sys.exit(1)
+    _protoc_path = protoc_list[0]
+  return _protoc_path
author	Allan Sandfeld Jensen <allan.jensen@qt.io>	2020-07-16 11:45:35 +0200
committer	Allan Sandfeld Jensen <allan.jensen@qt.io>	2020-07-17 08:59:23 +0000
commit	552906b0f222c5d5dd11b9fd73829d510980461a (patch)
tree	3a11e6ed0538a81dd83b20cf3a4783e297f26d91 /chromium/components/feed
parent	1b05827804eaf047779b597718c03e7d38344261 (diff)
download	qtwebengine-chromium-552906b0f222c5d5dd11b9fd73829d510980461a.tar.gz