BASELINE: Update Chromium to 77.0.3865.59

Change-Id: I1e89a5f3b009a9519a6705102ad65c92fe736f21
Reviewed-by: Michael Brüning <michael.bruning@qt.io>

15 files changed, 284 insertions, 159 deletions

diff --git a/chromium/tools/clang/OWNERS b/chromium/tools/clang/OWNERS
index 0da75e8fd25..9601fa4cfbc 100644
--- a/chromium/tools/clang/OWNERS
+++ b/chromium/tools/clang/OWNERS
@@ -1,4 +1,5 @@
 hans@chromium.org
+inglorion@chromium.org
 pcc@chromium.org
 thakis@chromium.org
 rnk@chromium.org
diff --git a/chromium/tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp b/chromium/tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp
index 3df46a3c413..7069f89ad51 100644
--- a/chromium/tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp
+++ b/chromium/tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.cpp
@@ -425,7 +425,7 @@ void BlinkGCPluginConsumer::CheckFinalization(RecordInfo* info) {
   // For finalized classes, check the finalization method if possible.
   if (info->IsGCFinalized()) {
     if (dtor && dtor->hasBody()) {
-      CheckFinalizerVisitor visitor(&cache_, info->IsEagerlyFinalized());
+      CheckFinalizerVisitor visitor(&cache_);
       visitor.TraverseCXXMethodDecl(dtor);
       if (!visitor.finalized_fields().empty()) {
         reporter_.FinalizerAccessesFinalizedFields(
diff --git a/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.cpp b/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.cpp
index 699b740e247..b435b00c7e5 100644
--- a/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.cpp
+++ b/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.cpp
@@ -12,50 +12,25 @@ namespace {
 // during finalization.
 class MightBeCollectedVisitor : public EdgeVisitor {
  public:
-  explicit MightBeCollectedVisitor(bool is_eagerly_finalized);
-
   bool might_be_collected() const;
-  bool as_eagerly_finalized() const;
 
   void VisitMember(Member* edge) override;
   void VisitCollection(Collection* edge) override;
 
  private:
-  bool might_be_collected_;
-  bool is_eagerly_finalized_;
-  bool as_eagerly_finalized_;
+  bool might_be_collected_ = false;
 };
 
-MightBeCollectedVisitor::MightBeCollectedVisitor(bool is_eagerly_finalized)
-    : might_be_collected_(false),
-      is_eagerly_finalized_(is_eagerly_finalized),
-      as_eagerly_finalized_(false) {
-}
-
 bool MightBeCollectedVisitor::might_be_collected() const {
   return might_be_collected_;
 }
 
-bool MightBeCollectedVisitor::as_eagerly_finalized() const {
-  return as_eagerly_finalized_;
-}
-
 void MightBeCollectedVisitor::VisitMember(Member* edge) {
-  if (is_eagerly_finalized_) {
-    if (edge->ptr()->IsValue()) {
-      Value* member = static_cast<Value*>(edge->ptr());
-      if (member->value()->IsEagerlyFinalized()) {
-        might_be_collected_ = true;
-        as_eagerly_finalized_ = true;
-      }
-    }
-    return;
-  }
   might_be_collected_ = true;
 }
 
 void MightBeCollectedVisitor::VisitCollection(Collection* edge) {
-  if (edge->on_heap() && !is_eagerly_finalized_) {
+  if (edge->on_heap()) {
     might_be_collected_ = true;
   } else {
     edge->AcceptMembers(this);
@@ -64,11 +39,9 @@ void MightBeCollectedVisitor::VisitCollection(Collection* edge) {
 
 }  // namespace
 
-CheckFinalizerVisitor::CheckFinalizerVisitor(RecordCache* cache,
-                                             bool is_eagerly_finalized)
+CheckFinalizerVisitor::CheckFinalizerVisitor(RecordCache* cache)
     : blacklist_context_(false),
-      cache_(cache),
-      is_eagerly_finalized_(is_eagerly_finalized) {
+      cache_(cache) {
 }
 
 CheckFinalizerVisitor::Errors& CheckFinalizerVisitor::finalized_fields() {
@@ -114,20 +87,17 @@ bool CheckFinalizerVisitor::VisitMemberExpr(MemberExpr* member) {
   if (seen_members_.find(member) != seen_members_.end())
     return true;
 
-  bool as_eagerly_finalized = false;
   if (blacklist_context_ &&
-      MightBeCollected(&it->second, &as_eagerly_finalized)) {
+      MightBeCollected(&it->second)) {
     finalized_fields_.push_back(
-        Error(member, as_eagerly_finalized, &it->second));
+        Error(member, &it->second));
     seen_members_.insert(member);
   }
   return true;
 }
 
-bool CheckFinalizerVisitor::MightBeCollected(FieldPoint* point,
-                                             bool* as_eagerly_finalized) {
-  MightBeCollectedVisitor visitor(is_eagerly_finalized_);
+bool CheckFinalizerVisitor::MightBeCollected(FieldPoint* point) {
+  MightBeCollectedVisitor visitor;
   point->edge()->Accept(&visitor);
-  *as_eagerly_finalized = visitor.as_eagerly_finalized();
   return visitor.might_be_collected();
 }
diff --git a/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.h b/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.h
index f926a0d14b0..74dfb1f1ca1 100644
--- a/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.h
+++ b/chromium/tools/clang/blink_gc_plugin/CheckFinalizerVisitor.h
@@ -22,20 +22,17 @@ class CheckFinalizerVisitor
  public:
   struct Error {
     Error(clang::MemberExpr* member,
-          bool as_eagerly_finalized,
           FieldPoint* field)
         : member(member),
-          as_eagerly_finalized(as_eagerly_finalized),
           field(field) {}
 
     clang::MemberExpr* member;
-    bool as_eagerly_finalized;
     FieldPoint* field;
   };
 
   typedef std::vector<Error> Errors;
 
-  CheckFinalizerVisitor(RecordCache* cache, bool is_eagerly_finalized);
+  explicit CheckFinalizerVisitor(RecordCache* cache);
 
   Errors& finalized_fields();
 
@@ -45,13 +42,12 @@ class CheckFinalizerVisitor
   bool VisitMemberExpr(clang::MemberExpr* member);
 
  private:
-  bool MightBeCollected(FieldPoint* point, bool* as_eagerly_finalized);
+  bool MightBeCollected(FieldPoint* point);
 
   bool blacklist_context_;
   Errors finalized_fields_;
   std::set<clang::MemberExpr*> seen_members_;
   RecordCache* cache_;
-  bool is_eagerly_finalized_;
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_CHECK_FINALIZER_VISITOR_H_
diff --git a/chromium/tools/clang/blink_gc_plugin/Config.cpp b/chromium/tools/clang/blink_gc_plugin/Config.cpp
index df8867a9b29..f2206660d70 100644
--- a/chromium/tools/clang/blink_gc_plugin/Config.cpp
+++ b/chromium/tools/clang/blink_gc_plugin/Config.cpp
@@ -22,7 +22,6 @@ const char kVisitorDispatcherName[] = "VisitorDispatcher";
 const char kVisitorVarName[] = "visitor";
 const char kAdjustAndMarkName[] = "AdjustAndMark";
 const char kIsHeapObjectAliveName[] = "IsHeapObjectAlive";
-const char kIsEagerlyFinalizedName[] = "IsEagerlyFinalizedMarker";
 const char kConstIteratorName[] = "const_iterator";
 const char kIteratorName[] = "iterator";
 const char kConstReverseIteratorName[] = "const_reverse_iterator";
diff --git a/chromium/tools/clang/blink_gc_plugin/Config.h b/chromium/tools/clang/blink_gc_plugin/Config.h
index f60594a5220..8aa85779f9b 100644
--- a/chromium/tools/clang/blink_gc_plugin/Config.h
+++ b/chromium/tools/clang/blink_gc_plugin/Config.h
@@ -29,7 +29,6 @@ extern const char kVisitorDispatcherName[];
 extern const char kVisitorVarName[];
 extern const char kAdjustAndMarkName[];
 extern const char kIsHeapObjectAliveName[];
-extern const char kIsEagerlyFinalizedName[];
 extern const char kConstIteratorName[];
 extern const char kIteratorName[];
 extern const char kConstReverseIteratorName[];
diff --git a/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.cpp b/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.cpp
index 1fa70aa7693..a1f9e08fada 100644
--- a/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.cpp
+++ b/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.cpp
@@ -49,9 +49,6 @@ const char kClassDoesNotRequireFinalization[] =
 const char kFinalizerAccessesFinalizedField[] =
     "[blink-gc] Finalizer %0 accesses potentially finalized field %1.";
 
-const char kFinalizerAccessesEagerlyFinalizedField[] =
-    "[blink-gc] Finalizer %0 accesses eagerly finalized field %1.";
-
 const char kRawPtrToGCManagedClassNote[] =
     "[blink-gc] Raw pointer field %0 to a GC managed class declared here:";
 
@@ -108,9 +105,6 @@ const char kMissingFinalizeDispatch[] =
 const char kFinalizedFieldNote[] =
     "[blink-gc] Potentially finalized field %0 declared here:";
 
-const char kEagerlyFinalizedFieldNote[] =
-    "[blink-gc] Field %0 having eagerly finalized value, declared here:";
-
 const char kUserDeclaredDestructorNote[] =
     "[blink-gc] User-declared destructor declared here:";
 
@@ -204,8 +198,6 @@ DiagnosticsReporter::DiagnosticsReporter(
       DiagnosticsEngine::Warning, kClassDoesNotRequireFinalization);
   diag_finalizer_accesses_finalized_field_ = diagnostic_.getCustomDiagID(
       getErrorLevel(), kFinalizerAccessesFinalizedField);
-  diag_finalizer_eagerly_finalized_field_ = diagnostic_.getCustomDiagID(
-      getErrorLevel(), kFinalizerAccessesEagerlyFinalizedField);
   diag_overridden_non_virtual_trace_ = diagnostic_.getCustomDiagID(
       getErrorLevel(), kOverriddenNonVirtualTrace);
   diag_missing_trace_dispatch_method_ = diagnostic_.getCustomDiagID(
@@ -262,8 +254,6 @@ DiagnosticsReporter::DiagnosticsReporter(
       DiagnosticsEngine::Note, kFieldContainsGCRootNote);
   diag_finalized_field_note_ = diagnostic_.getCustomDiagID(
       DiagnosticsEngine::Note, kFinalizedFieldNote);
-  diag_eagerly_finalized_field_note_ = diagnostic_.getCustomDiagID(
-      DiagnosticsEngine::Note, kEagerlyFinalizedFieldNote);
   diag_user_declared_destructor_note_ = diagnostic_.getCustomDiagID(
       DiagnosticsEngine::Note, kUserDeclaredDestructorNote);
   diag_user_declared_finalizer_note_ = diagnostic_.getCustomDiagID(
@@ -404,16 +394,10 @@ void DiagnosticsReporter::FinalizerAccessesFinalizedFields(
     CXXMethodDecl* dtor,
     const CheckFinalizerVisitor::Errors& errors) {
   for (auto& error : errors) {
-    bool as_eagerly_finalized = error.as_eagerly_finalized;
-    unsigned diag_error = as_eagerly_finalized ?
-                          diag_finalizer_eagerly_finalized_field_ :
-                          diag_finalizer_accesses_finalized_field_;
-    unsigned diag_note = as_eagerly_finalized ?
-                         diag_eagerly_finalized_field_note_ :
-                         diag_finalized_field_note_;
-    ReportDiagnostic(error.member->getBeginLoc(), diag_error)
+    ReportDiagnostic(error.member->getBeginLoc(),
+        diag_finalizer_accesses_finalized_field_)
         << dtor << error.field->field();
-    NoteField(error.field, diag_note);
+    NoteField(error.field, diag_finalized_field_note_);
   }
 }
 
diff --git a/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.h b/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.h
index 2d8b0c7ade1..b4e96d298d5 100644
--- a/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.h
+++ b/chromium/tools/clang/blink_gc_plugin/DiagnosticsReporter.h
@@ -114,7 +114,6 @@ class DiagnosticsReporter {
   unsigned diag_class_requires_finalization_;
   unsigned diag_class_does_not_require_finalization_;
   unsigned diag_finalizer_accesses_finalized_field_;
-  unsigned diag_finalizer_eagerly_finalized_field_;
   unsigned diag_overridden_non_virtual_trace_;
   unsigned diag_missing_trace_dispatch_method_;
   unsigned diag_missing_finalize_dispatch_method_;
@@ -142,7 +141,6 @@ class DiagnosticsReporter {
   unsigned diag_part_object_contains_gc_root_note_;
   unsigned diag_field_contains_gc_root_note_;
   unsigned diag_finalized_field_note_;
-  unsigned diag_eagerly_finalized_field_note_;
   unsigned diag_user_declared_destructor_note_;
   unsigned diag_user_declared_finalizer_note_;
   unsigned diag_base_requires_finalization_note_;
diff --git a/chromium/tools/clang/blink_gc_plugin/RecordInfo.cpp b/chromium/tools/clang/blink_gc_plugin/RecordInfo.cpp
index b86bb37aa74..487aa99f343 100644
--- a/chromium/tools/clang/blink_gc_plugin/RecordInfo.cpp
+++ b/chromium/tools/clang/blink_gc_plugin/RecordInfo.cpp
@@ -22,7 +22,6 @@ RecordInfo::RecordInfo(CXXRecordDecl* record, RecordCache* cache)
       does_need_finalization_(kNotComputed),
       has_gc_mixin_methods_(kNotComputed),
       is_declaring_local_trace_(kNotComputed),
-      is_eagerly_finalized_(kNotComputed),
       determined_trace_methods_(false),
       trace_method_(0),
       trace_dispatch_method_(0),
@@ -198,25 +197,6 @@ bool RecordInfo::IsGCAllocated() {
   return IsGCDerived() || IsHeapAllocatedCollection();
 }
 
-bool RecordInfo::IsEagerlyFinalized() {
-  if (is_eagerly_finalized_ != kNotComputed)
-    return is_eagerly_finalized_;
-
-  is_eagerly_finalized_ = kFalse;
-  if (!IsGCFinalized())
-    return is_eagerly_finalized_;
-
-  for (Decl* decl : record_->decls()) {
-    if (TypedefDecl* typedef_decl = dyn_cast<TypedefDecl>(decl)) {
-      if (typedef_decl->getNameAsString() != kIsEagerlyFinalizedName)
-        continue;
-      is_eagerly_finalized_ = kTrue;
-      break;
-    }
-  }
-  return is_eagerly_finalized_;
-}
-
 bool RecordInfo::HasDefinition() {
   return record_->hasDefinition();
 }
diff --git a/chromium/tools/clang/blink_gc_plugin/RecordInfo.h b/chromium/tools/clang/blink_gc_plugin/RecordInfo.h
index ec510f38680..6f1c31be482 100644
--- a/chromium/tools/clang/blink_gc_plugin/RecordInfo.h
+++ b/chromium/tools/clang/blink_gc_plugin/RecordInfo.h
@@ -103,7 +103,6 @@ class RecordInfo {
   bool IsStackAllocated();
   bool IsNonNewable();
   bool IsOnlyPlacementNewable();
-  bool IsEagerlyFinalized();
 
   bool HasDefinition();
 
@@ -148,7 +147,6 @@ class RecordInfo {
   CachedBool does_need_finalization_;
   CachedBool has_gc_mixin_methods_;
   CachedBool is_declaring_local_trace_;
-  CachedBool is_eagerly_finalized_;
 
   bool determined_trace_methods_;
   clang::CXXMethodDecl* trace_method_;
diff --git a/chromium/tools/clang/scripts/build.py b/chromium/tools/clang/scripts/build.py
index 7849efd0cc1..4637e56d80d 100755
--- a/chromium/tools/clang/scripts/build.py
+++ b/chromium/tools/clang/scripts/build.py
@@ -24,9 +24,9 @@ import sys
 
 from update import (CDS_URL, CHROMIUM_DIR, CLANG_REVISION, LLVM_BUILD_DIR,
                     FORCE_HEAD_REVISION_FILE, PACKAGE_VERSION, RELEASE_VERSION,
-                    STAMP_FILE, CopyFile, CopyDiaDllTo, DownloadAndUnpack,
-                    EnsureDirExists, GetWinSDKDir, ReadStampFile, RmTree,
-                    WriteStampFile)
+                    STAMP_FILE, CopyFile, CopyDiaDllTo, DownloadUrl,
+                    DownloadAndUnpack, EnsureDirExists, GetWinSDKDir,
+                    ReadStampFile, RmTree, WriteStampFile)
 
 
 # Path constants. (All of these should be absolute paths.)
@@ -36,6 +36,8 @@ COMPILER_RT_DIR = os.path.join(LLVM_DIR, 'compiler-rt')
 LLVM_BOOTSTRAP_DIR = os.path.join(THIRD_PARTY_DIR, 'llvm-bootstrap')
 LLVM_BOOTSTRAP_INSTALL_DIR = os.path.join(THIRD_PARTY_DIR,
                                           'llvm-bootstrap-install')
+LLVM_INSTRUMENTED_DIR = os.path.join(THIRD_PARTY_DIR, 'llvm-instrumented')
+LLVM_PROFDATA_FILE = os.path.join(LLVM_INSTRUMENTED_DIR, 'profdata.prof')
 CHROME_TOOLS_SHIM_DIR = os.path.join(LLVM_DIR, 'llvm', 'tools', 'chrometools')
 THREADS_ENABLED_BUILD_DIR = os.path.join(THIRD_PARTY_DIR,
                                          'llvm-threads-enabled')
@@ -47,7 +49,8 @@ ANDROID_NDK_DIR = os.path.join(
 FUCHSIA_SDK_DIR = os.path.join(CHROMIUM_DIR, 'third_party', 'fuchsia-sdk',
                                'sdk')
 
-BUG_REPORT_URL = ('https://crbug.com and run tools/clang/scripts/upload_crash.py'
+BUG_REPORT_URL = ('https://crbug.com and run'
+                  ' tools/clang/scripts/process_crashreports.py'
                   ' (only works inside Google) which will upload a report')
 
 
@@ -95,8 +98,8 @@ def CopyDirectoryContents(src, dst):
 def CheckoutLLVM(commit, dir):
   """Checkout the LLVM monorepo at a certain git commit in dir. Any local
   modifications in dir will be lost."""
-  print("Checking out LLVM monorepo %s into '%s'" % (commit, dir))
 
+  print('Checking out LLVM monorepo %s into %s' % (commit, dir))
   git_dir = os.path.join(dir, '.git')
   fetch_cmd = ['git', '--git-dir', git_dir, 'fetch']
   checkout_cmd = ['git', 'checkout', commit]
@@ -116,7 +119,7 @@ def CheckoutLLVM(commit, dir):
 
   # Otherwise, do a fresh clone.
   if os.path.isdir(dir):
-    print("Removing %s." % dir)
+    print('Removing %s.' % dir)
     RmTree(dir)
   if RunCommand(clone_cmd, fail_hard=False):
     os.chdir(dir)
@@ -209,7 +212,7 @@ def AddGnuWinToPath():
     return
 
   gnuwin_dir = os.path.join(LLVM_BUILD_TOOLS_DIR, 'gnuwin')
-  GNUWIN_VERSION = '11'
+  GNUWIN_VERSION = '12'
   GNUWIN_STAMP = os.path.join(gnuwin_dir, 'stamp')
   if ReadStampFile(GNUWIN_STAMP) == GNUWIN_VERSION:
     print('GNU Win tools already up to date.')
@@ -232,6 +235,16 @@ def AddGnuWinToPath():
     f.write('group: files\n')
 
 
+def MaybeDownloadHostGcc(args):
+  """Download a modern GCC host compiler on Linux."""
+  if not sys.platform.startswith('linux') or args.gcc_toolchain:
+    return
+  gcc_dir = os.path.join(LLVM_BUILD_TOOLS_DIR, 'gcc510trusty')
+  if not os.path.exists(gcc_dir):
+    DownloadAndUnpack(CDS_URL + '/tools/gcc510trusty.tgz', gcc_dir)
+  args.gcc_toolchain = gcc_dir
+
+
 def SetMacXcodePath():
   """Set DEVELOPER_DIR to the path to hermetic Xcode.app on Mac OS X."""
   if sys.platform != 'darwin':
@@ -258,6 +271,37 @@ def VerifyVersionOfBuiltClangMatchesVERSION():
     sys.exit(1)
 
 
+def CopyLibstdcpp(args, build_dir):
+  if not args.gcc_toolchain:
+    return
+  # Find libstdc++.so.6
+  libstdcpp = subprocess.check_output(
+      [os.path.join(args.gcc_toolchain, 'bin', 'g++'),
+       '-print-file-name=libstdc++.so.6']).rstrip()
+
+  # Copy libstdc++.so.6 into the build dir so that the built binaries can find
+  # it. Binaries get their rpath set to $origin/../lib/. For clang, lld,
+  # etc. that live in the bin/ directory, this means they expect to find the .so
+  # in their neighbouring lib/ dir. For other tools however, this doesn't work
+  # since those exeuctables are spread out into different directories.
+  # TODO(hans): Unit tests don't get rpath set at all, unittests/ copying
+  # below doesn't help at the moment.
+  for d in ['lib',
+            'test/tools/llvm-isel-fuzzer/lib',
+            'test/tools/llvm-opt-fuzzer/lib',
+            'unittests/CodeGen/lib',
+            'unittests/DebugInfo/lib',
+            'unittests/ExecutionEngine/lib',
+            'unittests/Support/lib',
+            'unittests/Target/lib',
+            'unittests/Transforms/lib',
+            'unittests/lib',
+            'unittests/tools/lib',
+            'unittests/tools/llvm-exegesis/lib']:
+    EnsureDirExists(os.path.join(build_dir, d))
+    CopyFile(libstdcpp, os.path.join(build_dir, d))
+
+
 def gn_arg(v):
   if v == 'True':
     return True
@@ -273,9 +317,12 @@ def main():
                       help='first build clang with CC, then with itself.')
   parser.add_argument('--disable-asserts', action='store_true',
                       help='build with asserts disabled')
-  parser.add_argument('--gcc-toolchain', help='(no longer used)')
+  parser.add_argument('--gcc-toolchain', help='what gcc toolchain to use for '
+                      'building; --gcc-toolchain=/opt/foo picks '
+                      '/opt/foo/bin/gcc')
   parser.add_argument('--lto-lld', action='store_true',
                       help='build lld with LTO (only applies on Linux)')
+  parser.add_argument('--pgo', action='store_true', help='build with PGO')
   parser.add_argument('--llvm-force-head-revision', action='store_true',
                       help='build the latest revision')
   parser.add_argument('--run-tests', action='store_true',
@@ -301,6 +348,15 @@ def main():
                       default=sys.platform in ('linux2', 'darwin'))
   args = parser.parse_args()
 
+  # TODO(crbug.com/985289): Remove when rolling past r366427.
+  if args.llvm_force_head_revision:
+    global RELEASE_VERSION
+    RELEASE_VERSION = '10.0.0'
+    old_lib_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang', '9.0.0')
+    if (os.path.isdir(old_lib_dir)):
+      print('Removing old lib dir: ' + old_lib_dir)
+      RmTree(old_lib_dir)
+
   if args.lto_lld and not args.bootstrap:
     print('--lto-lld requires --bootstrap')
     return 1
@@ -308,6 +364,9 @@ def main():
     # TODO(hans): Use it on Windows too.
     print('--lto-lld is only effective on Linux. Ignoring the option.')
     args.lto_lld = False
+  if args.pgo and not args.bootstrap:
+    print('--pgo requires --bootstrap')
+    return 1
   if args.with_android and not os.path.exists(ANDROID_NDK_DIR):
     print('Android NDK not found at ' + ANDROID_NDK_DIR)
     print('The Android NDK is needed to build a Clang whose -fsanitize=address')
@@ -337,6 +396,10 @@ def main():
   # move this down to where we fetch other build tools.
   AddGnuWinToPath()
 
+  # TODO(crbug.com/929645): Remove once we build on host systems with a modern
+  # enough GCC to build Clang.
+  MaybeDownloadHostGcc(args)
+
   global CLANG_REVISION, PACKAGE_VERSION
   if args.llvm_force_head_revision:
     CLANG_REVISION = GetLatestLLVMCommit()
@@ -363,7 +426,20 @@ def main():
   if args.skip_build:
     return 0
 
-  cc, cxx = None, None
+  # The variable "lld" is only used on Windows because only there does setting
+  # CMAKE_LINKER have an effect: On Windows, the linker is called directly,
+  # while elsewhere it's called through the compiler driver, and we pass
+  # -fuse-ld=lld there to make the compiler driver call the linker (by setting
+  # LLVM_ENABLE_LLD).
+  cc, cxx, lld = None, None, None
+
+  if args.gcc_toolchain:
+    # Use the specified gcc installation for building.
+    cc = os.path.join(args.gcc_toolchain, 'bin', 'gcc')
+    cxx = os.path.join(args.gcc_toolchain, 'bin', 'g++')
+    if not os.access(cc, os.X_OK):
+      print('Invalid --gcc-toolchain: ' + args.gcc_toolchain)
+      return 1
 
   cflags = []
   cxxflags = []
@@ -390,13 +466,20 @@ def main():
                      '-DCLANG_PLUGIN_SUPPORT=OFF',
                      '-DCLANG_ENABLE_STATIC_ANALYZER=OFF',
                      '-DCLANG_ENABLE_ARCMT=OFF',
-                     # TODO(crbug.com/929645): Use newer toolchain to host.
-                     '-DLLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN=ON',
                      '-DBUG_REPORT_URL=' + BUG_REPORT_URL,
                      # See PR41956: Don't link libcxx into libfuzzer.
                      '-DCOMPILER_RT_USE_LIBCXX=NO',
+                     # Don't run Go bindings tests; PGO makes them confused.
+                     '-DLLVM_INCLUDE_GO_TESTS=OFF',
                      ]
 
+  if args.gcc_toolchain:
+    # Don't use the custom gcc toolchain when building compiler-rt tests; those
+    # tests are built with the just-built Clang, and target both i386 and x86_64
+    # for example, so should ust the system's libstdc++.
+    base_cmake_args.append(
+        '-DCOMPILER_RT_TEST_COMPILER_CFLAGS=--gcc-toolchain=')
+
   if sys.platform == 'win32':
     base_cmake_args.append('-DLLVM_USE_CRT_RELEASE=MT')
 
@@ -418,7 +501,10 @@ def main():
     os.chdir(LLVM_BOOTSTRAP_DIR)
 
     projects = 'clang'
-    if args.lto_lld:
+    if args.pgo:
+      # Need libclang_rt.profile
+      projects += ';compiler-rt'
+    if sys.platform != 'darwin' or args.lto_lld:
       projects += ';lld'
     if sys.platform == 'darwin':
       # Need libc++ and compiler-rt for the bootstrap compiler on mac.
@@ -447,41 +533,131 @@ def main():
           '-DCOMPILER_RT_BUILD_BUILTINS=ON',
           '-DCOMPILER_RT_BUILD_CRT=OFF',
           '-DCOMPILER_RT_BUILD_LIBFUZZER=OFF',
-          '-DCOMPILER_RT_BUILD_PROFILE=OFF',
           '-DCOMPILER_RT_BUILD_SANITIZERS=OFF',
           '-DCOMPILER_RT_BUILD_XRAY=OFF',
           '-DCOMPILER_RT_ENABLE_IOS=OFF',
           '-DCOMPILER_RT_ENABLE_WATCHOS=OFF',
           '-DCOMPILER_RT_ENABLE_TVOS=OFF',
           ])
+    elif args.pgo:
+      # PGO needs libclang_rt.profile but none of the other compiler-rt stuff.
+      bootstrap_args.extend([
+          '-DCOMPILER_RT_BUILD_BUILTINS=OFF',
+          '-DCOMPILER_RT_BUILD_CRT=OFF',
+          '-DCOMPILER_RT_BUILD_LIBFUZZER=OFF',
+          '-DCOMPILER_RT_BUILD_PROFILE=ON',
+          '-DCOMPILER_RT_BUILD_SANITIZERS=OFF',
+          '-DCOMPILER_RT_BUILD_XRAY=OFF',
+          ])
+
     if cc is not None:  bootstrap_args.append('-DCMAKE_C_COMPILER=' + cc)
     if cxx is not None: bootstrap_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
+    if lld is not None: bootstrap_args.append('-DCMAKE_LINKER=' + lld)
     RunCommand(['cmake'] + bootstrap_args + [os.path.join(LLVM_DIR, 'llvm')],
                msvc_arch='x64')
+    CopyLibstdcpp(args, LLVM_BOOTSTRAP_DIR)
+    CopyLibstdcpp(args, LLVM_BOOTSTRAP_INSTALL_DIR)
     RunCommand(['ninja'], msvc_arch='x64')
     if args.run_tests:
+      test_targets = [ 'check-all' ]
+      if sys.platform == 'darwin':
+        # TODO(crbug.com/731375): Run check-all on Darwin too.
+        test_targets = [ 'check-llvm', 'check-clang', 'check-builtins' ]
       if sys.platform == 'win32':
         CopyDiaDllTo(os.path.join(LLVM_BOOTSTRAP_DIR, 'bin'))
-      RunCommand(['ninja', 'check-all'], msvc_arch='x64')
+      RunCommand(['ninja'] + test_targets, msvc_arch='x64')
     RunCommand(['ninja', 'install'], msvc_arch='x64')
 
     if sys.platform == 'win32':
       cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
       cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang-cl.exe')
+      lld = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'lld-link.exe')
       # CMake has a hard time with backslashes in compiler paths:
       # https://stackoverflow.com/questions/13050827
       cc = cc.replace('\\', '/')
       cxx = cxx.replace('\\', '/')
+      lld = lld.replace('\\', '/')
     else:
       cc = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang')
       cxx = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'clang++')
+    if sys.platform.startswith('linux'):
+      base_cmake_args.append('-DLLVM_ENABLE_LLD=ON')
+
+    if args.gcc_toolchain:
+      # Tell the bootstrap compiler where to find the standard library headers
+      # and shared object files.
+      cflags.append('--gcc-toolchain=' + args.gcc_toolchain)
+      cxxflags.append('--gcc-toolchain=' + args.gcc_toolchain)
+
+    print('Bootstrap compiler installed.')
+
+  if args.pgo:
+    print('Building instrumented compiler')
+    if os.path.exists(LLVM_INSTRUMENTED_DIR):
+      RmTree(LLVM_INSTRUMENTED_DIR)
+    EnsureDirExists(LLVM_INSTRUMENTED_DIR)
+    os.chdir(LLVM_INSTRUMENTED_DIR)
+
+    projects = 'clang'
+    if sys.platform == 'darwin':
+      projects += ';libcxx;compiler-rt'
 
-    print('Bootstrap compiler installed; building final compiler.')
+    instrument_args = base_cmake_args + [
+        '-DLLVM_ENABLE_THREADS=OFF',
+        '-DLLVM_ENABLE_PROJECTS=' + projects,
+        '-DCMAKE_C_FLAGS=' + ' '.join(cflags),
+        '-DCMAKE_CXX_FLAGS=' + ' '.join(cxxflags),
+        # Build with instrumentation.
+        '-DLLVM_BUILD_INSTRUMENTED=IR',
+        ]
+    # Build with the bootstrap compiler.
+    if cc is not None:  instrument_args.append('-DCMAKE_C_COMPILER=' + cc)
+    if cxx is not None: instrument_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
+    if lld is not None: instrument_args.append('-DCMAKE_LINKER=' + lld)
 
+    RunCommand(['cmake'] + instrument_args + [os.path.join(LLVM_DIR, 'llvm')],
+               msvc_arch='x64')
+    CopyLibstdcpp(args, LLVM_INSTRUMENTED_DIR)
+    RunCommand(['ninja'], msvc_arch='x64')
+    print('Instrumented compiler built.')
+
+    # Train by building some C++ code.
+    #
+    # pgo_training-1.ii is a preprocessed (on Linux) version of
+    # src/third_party/blink/renderer/core/layout/layout_object.cc, selected
+    # because it's a large translation unit in Blink, which is normally the
+    # slowest part of Chromium to compile. Using this, we get ~20% shorter
+    # build times for Linux, Android, and Mac, which is also what we got when
+    # training by actually building a target in Chromium. (For comparison, a
+    # C++-y "Hello World" program only resulted in 14% faster builds.)
+    # See https://crbug.com/966403#c16 for all numbers.
+    #
+    # TODO(hans): Enhance the training, perhaps by including preprocessed code
+    # from more platforms, and by doing some linking so that lld can benefit
+    # from PGO as well. Perhaps the training could be done asynchronously by
+    # dedicated buildbots that upload profiles to the cloud.
+    training_source = 'pgo_training-1.ii'
+    with open(training_source, 'w') as f:
+      DownloadUrl(CDS_URL + '/' + training_source, f)
+    train_cmd = [os.path.join(LLVM_INSTRUMENTED_DIR, 'bin', 'clang++'),
+                '-target', 'x86_64-unknown-unknown', '-O2', '-g', '-std=c++14',
+                 '-fno-exceptions', '-fno-rtti', '-w', '-c', training_source]
+    if sys.platform == 'darwin':
+      train_cmd.extend(['-stdlib=libc++', '-isysroot',
+                        subprocess.check_output(['xcrun',
+                                                 '--show-sdk-path']).rstrip()])
+    RunCommand(train_cmd, msvc_arch='x64')
+
+    # Merge profiles.
+    profdata = os.path.join(LLVM_BOOTSTRAP_INSTALL_DIR, 'bin', 'llvm-profdata')
+    RunCommand([profdata, 'merge', '-output=' + LLVM_PROFDATA_FILE] +
+                glob.glob(os.path.join(LLVM_INSTRUMENTED_DIR, 'profiles',
+                                       '*.profraw')), msvc_arch='x64')
+    print('Profile generated.')
 
   compiler_rt_args = [
     '-DCOMPILER_RT_BUILD_CRT=OFF',
-    '-DCOMPILER_RT_BUILD_LIBFUZZER=ON',
+    '-DCOMPILER_RT_BUILD_LIBFUZZER=OFF',
     '-DCOMPILER_RT_BUILD_PROFILE=ON',
     '-DCOMPILER_RT_BUILD_SANITIZERS=ON',
     '-DCOMPILER_RT_BUILD_XRAY=OFF',
@@ -501,12 +677,6 @@ def main():
         ])
   else:
     compiler_rt_args.append('-DCOMPILER_RT_BUILD_BUILTINS=OFF')
-  if sys.platform.startswith('linux'):
-    # Only build the 64-bit runtime, we don't need the 32-bit one.
-    compiler_rt_args.extend([
-        '-DCMAKE_C_COMPILER_TARGET=x86_64-unknown-linux-gnu',
-        '-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON',
-    ])
 
   # LLVM uses C++11 starting in llvm 3.5. On Linux, this means libstdc++4.7+ is
   # needed, on OS X it requires libc++. clang only automatically links to libc++
@@ -544,6 +714,7 @@ def main():
 
   # Build lld and code coverage tools. This is done separately from the rest of
   # the build because these tools require threading support.
+  print('Building thread-enabled tools.')
   tools_with_threading = [ 'dsymutil', 'lld', 'llvm-cov', 'llvm-profdata' ]
   print('Building the following tools with threading support: %s' %
         str(tools_with_threading))
@@ -563,6 +734,8 @@ def main():
     threads_enabled_cmake_args.append('-DCMAKE_C_COMPILER=' + cc)
   if cxx is not None:
     threads_enabled_cmake_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
+  if lld is not None:
+    threads_enabled_cmake_args.append('-DCMAKE_LINKER=' + lld)
 
   if args.lto_lld:
     # Build lld with LTO. That speeds up the linker by ~10%.
@@ -578,17 +751,21 @@ def main():
         '-DCMAKE_AR=' + ar,
         '-DCMAKE_RANLIB=' + ranlib,
         '-DLLVM_ENABLE_LTO=thin',
-        '-DLLVM_USE_LINKER=lld']
+        ]
 
   RunCommand(['cmake'] + threads_enabled_cmake_args +
              [os.path.join(LLVM_DIR, 'llvm')],
              msvc_arch='x64', env=deployment_env)
+  CopyLibstdcpp(args, THREADS_ENABLED_BUILD_DIR)
   RunCommand(['ninja'] + tools_with_threading, msvc_arch='x64')
 
+  print('Building final compiler.')
+
   default_tools = ['plugins', 'blink_gc_plugin', 'translation_unit']
   chrome_tools = list(set(default_tools + args.extra_tools))
   if cc is not None:  base_cmake_args.append('-DCMAKE_C_COMPILER=' + cc)
   if cxx is not None: base_cmake_args.append('-DCMAKE_CXX_COMPILER=' + cxx)
+  if lld is not None: base_cmake_args.append('-DCMAKE_LINKER=' + lld)
   cmake_args = base_cmake_args + compiler_rt_args + [
       '-DLLVM_ENABLE_THREADS=OFF',
       '-DCMAKE_C_FLAGS=' + ' '.join(cflags),
@@ -599,6 +776,8 @@ def main():
       '-DCMAKE_INSTALL_PREFIX=' + LLVM_BUILD_DIR,
       '-DCHROMIUM_TOOLS_SRC=%s' % os.path.join(CHROMIUM_DIR, 'tools', 'clang'),
       '-DCHROMIUM_TOOLS=%s' % ';'.join(chrome_tools)]
+  if args.pgo:
+    cmake_args.append('-DLLVM_PROFDATA_FILE=' + LLVM_PROFDATA_FILE)
   if sys.platform == 'darwin':
     cmake_args += ['-DCOMPILER_RT_ENABLE_IOS=ON',
                    '-DSANITIZER_MIN_OSX_VERSION=10.7']
@@ -612,6 +791,7 @@ def main():
   os.chdir(LLVM_BUILD_DIR)
   RunCommand(['cmake'] + cmake_args + [os.path.join(LLVM_DIR, 'llvm')],
              msvc_arch='x64', env=deployment_env)
+  CopyLibstdcpp(args, LLVM_BUILD_DIR)
   RunCommand(['ninja'], msvc_arch='x64')
 
   # Copy in the threaded versions of lld and other tools.
@@ -724,12 +904,12 @@ def main():
         '-DCMAKE_C_FLAGS=' + ' '.join(cflags),
         '-DCMAKE_CXX_FLAGS=' + ' '.join(cflags),
         '-DCMAKE_ASM_FLAGS=' + ' '.join(cflags),
-        "-DCOMPILER_RT_BUILD_BUILTINS=OFF",
-        "-DCOMPILER_RT_BUILD_CRT=OFF",
-        "-DCOMPILER_RT_BUILD_LIBFUZZER=OFF",
-        "-DCOMPILER_RT_BUILD_PROFILE=ON",
-        "-DCOMPILER_RT_BUILD_SANITIZERS=ON",
-        "-DCOMPILER_RT_BUILD_XRAY=OFF",
+        '-DCOMPILER_RT_BUILD_BUILTINS=OFF',
+        '-DCOMPILER_RT_BUILD_CRT=OFF',
+        '-DCOMPILER_RT_BUILD_LIBFUZZER=OFF',
+        '-DCOMPILER_RT_BUILD_PROFILE=ON',
+        '-DCOMPILER_RT_BUILD_SANITIZERS=ON',
+        '-DCOMPILER_RT_BUILD_XRAY=OFF',
         '-DSANITIZER_CXX_ABI=libcxxabi',
         '-DCMAKE_SHARED_LINKER_FLAGS=-Wl,-u__cxa_demangle',
         '-DANDROID=1']
@@ -775,12 +955,12 @@ def main():
         '-DCMAKE_SYSTEM_NAME=Fuchsia',
         '-DCMAKE_C_COMPILER_TARGET=%s-fuchsia' % target_arch,
         '-DCMAKE_ASM_COMPILER_TARGET=%s-fuchsia' % target_arch,
-        "-DCOMPILER_RT_BUILD_BUILTINS=ON",
-        "-DCOMPILER_RT_BUILD_CRT=OFF",
-        "-DCOMPILER_RT_BUILD_LIBFUZZER=OFF",
-        "-DCOMPILER_RT_BUILD_PROFILE=OFF",
-        "-DCOMPILER_RT_BUILD_SANITIZERS=OFF",
-        "-DCOMPILER_RT_BUILD_XRAY=OFF",
+        '-DCOMPILER_RT_BUILD_BUILTINS=ON',
+        '-DCOMPILER_RT_BUILD_CRT=OFF',
+        '-DCOMPILER_RT_BUILD_LIBFUZZER=OFF',
+        '-DCOMPILER_RT_BUILD_PROFILE=OFF',
+        '-DCOMPILER_RT_BUILD_SANITIZERS=OFF',
+        '-DCOMPILER_RT_BUILD_XRAY=OFF',
         '-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON',
         '-DCMAKE_SYSROOT=%s' % toolchain_dir,
         # TODO(thakis|scottmg): Use PER_TARGET_RUNTIME_DIR for all platforms.
@@ -801,10 +981,10 @@ def main():
 
       # And copy it into the main build tree.
       fuchsia_lib_dst_dir = os.path.join(LLVM_BUILD_DIR, 'lib', 'clang',
-                                         RELEASE_VERSION, target_spec, 'lib')
+                                         RELEASE_VERSION, 'lib', target_spec)
       if not os.path.exists(fuchsia_lib_dst_dir):
         os.makedirs(fuchsia_lib_dst_dir)
-      CopyFile(os.path.join(build_dir, target_spec, 'lib', builtins_a),
+      CopyFile(os.path.join(build_dir, 'lib', target_spec, builtins_a),
                fuchsia_lib_dst_dir)
 
   # Run tests.
diff --git a/chromium/tools/clang/scripts/package.py b/chromium/tools/clang/scripts/package.py
index 0af8d1666bc..68ccd3046bd 100755
--- a/chromium/tools/clang/scripts/package.py
+++ b/chromium/tools/clang/scripts/package.py
@@ -15,7 +15,7 @@ import subprocess
 import sys
 import tarfile
 
-from update import RELEASE_VERSION
+from update import RELEASE_VERSION, STAMP_FILE
 
 # Path constants.
 THIS_DIR = os.path.dirname(__file__)
@@ -30,7 +30,6 @@ LLVM_BUILD_DIR = os.path.join(THIRD_PARTY_DIR, 'llvm-build')
 LLVM_RELEASE_DIR = os.path.join(LLVM_BUILD_DIR, 'Release+Asserts')
 EU_STRIP = os.path.join(BUILDTOOLS_DIR, 'third_party', 'eu-strip', 'bin',
                         'eu-strip')
-STAMP_FILE = os.path.join(LLVM_BUILD_DIR, 'cr_build_revision')
 
 
 def Tee(output, logfile):
@@ -193,12 +192,14 @@ def main():
     shutil.rmtree(LLVM_BOOTSTRAP_INSTALL_DIR, ignore_errors=True)
     shutil.rmtree(LLVM_BUILD_DIR, ignore_errors=True)
 
-    opt_flags = []
-    if sys.platform.startswith('linux'):
-      opt_flags += ['--lto-lld']
     build_cmd = [sys.executable, os.path.join(THIS_DIR, 'build.py'),
                  '--bootstrap', '--disable-asserts',
-                 '--run-tests'] + opt_flags
+                 '--run-tests']
+    if sys.platform != 'win32':
+      # TODO(hans): Use --pgo for the Windows package too.
+      build_cmd.append('--pgo')
+    if sys.platform.startswith('linux'):
+      build_cmd.append('--lto-lld')
     TeeCmd(build_cmd, log)
 
   stamp = open(STAMP_FILE).read().rstrip()
@@ -231,8 +232,8 @@ def main():
       'bin/clang',
 
       # Include libclang_rt.builtins.a for Fuchsia targets.
-      'lib/clang/$V/aarch64-fuchsia/lib/libclang_rt.builtins.a',
-      'lib/clang/$V/x86_64-fuchsia/lib/libclang_rt.builtins.a',
+      'lib/clang/$V/lib/aarch64-fuchsia/libclang_rt.builtins.a',
+      'lib/clang/$V/lib/x86_64-fuchsia/libclang_rt.builtins.a',
     ])
   if sys.platform == 'darwin':
     want.extend([
@@ -240,9 +241,6 @@ def main():
       'lib/clang/$V/lib/darwin/libclang_rt.asan_iossim_dynamic.dylib',
       'lib/clang/$V/lib/darwin/libclang_rt.asan_osx_dynamic.dylib',
 
-      # Fuzzing instrumentation (-fsanitize=fuzzer-no-link).
-      'lib/clang/$V/lib/darwin/libclang_rt.fuzzer_no_main_osx.a',
-
       # OS X and iOS builtin libraries (iossim is lipo'd into ios) for the
       # _IsOSVersionAtLeast runtime function.
       'lib/clang/$V/lib/darwin/libclang_rt.ios.a',
@@ -254,16 +252,25 @@ def main():
     ])
   elif sys.platform.startswith('linux'):
     want.extend([
+      # Copy the stdlibc++.so.6 we linked the binaries against.
+      'lib/libstdc++.so.6',
+
+      # Add LLD.
       'bin/lld',
 
       # Add llvm-ar for LTO.
       'bin/llvm-ar',
 
+      # Add llvm-objcopy for partition extraction on Android.
+      'bin/llvm-objcopy',
+
       # AddressSanitizer C runtime (pure C won't link with *_cxx).
+      'lib/clang/$V/lib/linux/libclang_rt.asan-i386.a',
       'lib/clang/$V/lib/linux/libclang_rt.asan-x86_64.a',
       'lib/clang/$V/lib/linux/libclang_rt.asan-x86_64.a.syms',
 
       # AddressSanitizer C++ runtime.
+      'lib/clang/$V/lib/linux/libclang_rt.asan_cxx-i386.a',
       'lib/clang/$V/lib/linux/libclang_rt.asan_cxx-x86_64.a',
       'lib/clang/$V/lib/linux/libclang_rt.asan_cxx-x86_64.a.syms',
 
@@ -272,9 +279,6 @@ def main():
       'lib/clang/$V/lib/linux/libclang_rt.asan-arm-android.so',
       'lib/clang/$V/lib/linux/libclang_rt.asan-i686-android.so',
 
-      # Fuzzing instrumentation (-fsanitize=fuzzer-no-link).
-      'lib/clang/$V/lib/linux/libclang_rt.fuzzer_no_main-x86_64.a',
-
       # HWASAN Android runtime.
       'lib/clang/$V/lib/linux/libclang_rt.hwasan-aarch64-android.so',
 
@@ -287,6 +291,7 @@ def main():
       'lib/clang/$V/lib/linux/libclang_rt.msan_cxx-x86_64.a.syms',
 
       # Profile runtime (used by profiler and code coverage).
+      'lib/clang/$V/lib/linux/libclang_rt.profile-i386.a',
       'lib/clang/$V/lib/linux/libclang_rt.profile-x86_64.a',
       'lib/clang/$V/lib/linux/libclang_rt.profile-aarch64-android.a',
       'lib/clang/$V/lib/linux/libclang_rt.profile-arm-android.a',
@@ -300,10 +305,12 @@ def main():
       'lib/clang/$V/lib/linux/libclang_rt.tsan_cxx-x86_64.a.syms',
 
       # UndefinedBehaviorSanitizer C runtime (pure C won't link with *_cxx).
+      'lib/clang/$V/lib/linux/libclang_rt.ubsan_standalone-i386.a',
       'lib/clang/$V/lib/linux/libclang_rt.ubsan_standalone-x86_64.a',
       'lib/clang/$V/lib/linux/libclang_rt.ubsan_standalone-x86_64.a.syms',
 
       # UndefinedBehaviorSanitizer C++ runtime.
+      'lib/clang/$V/lib/linux/libclang_rt.ubsan_standalone_cxx-i386.a',
       'lib/clang/$V/lib/linux/libclang_rt.ubsan_standalone_cxx-x86_64.a',
       'lib/clang/$V/lib/linux/libclang_rt.ubsan_standalone_cxx-x86_64.a.syms',
 
@@ -322,9 +329,6 @@ def main():
       # AddressSanitizer C++ runtime.
       'lib/clang/$V/lib/windows/clang_rt.asan_cxx-x86_64.lib',
 
-      # Fuzzing instrumentation (-fsanitize=fuzzer-no-link).
-      'lib/clang/$V/lib/windows/clang_rt.fuzzer_no_main-x86_64.lib',
-
       # Thunk for AddressSanitizer needed for static build of a shared lib.
       'lib/clang/$V/lib/windows/clang_rt.asan_dll_thunk-x86_64.lib',
 
@@ -384,6 +388,7 @@ def main():
   if sys.platform.startswith('linux'):
     stripped_binaries.append('lld')
     stripped_binaries.append('llvm-ar')
+    stripped_binaries.append('llvm-objcopy')
   for f in stripped_binaries:
     if sys.platform != 'win32':
       subprocess.call(['strip', os.path.join(pdir, 'bin', f)])
diff --git a/chromium/tools/clang/scripts/update.py b/chromium/tools/clang/scripts/update.py
index 082dc5ec7ac..614e9573639 100755
--- a/chromium/tools/clang/scripts/update.py
+++ b/chromium/tools/clang/scripts/update.py
@@ -14,6 +14,7 @@ near-tip-of-tree clang version:
 
 # TODO: Running stand-alone won't work on Windows due to the dia dll copying.
 
+from __future__ import division
 from __future__ import print_function
 import argparse
 import os
@@ -25,10 +26,10 @@ import tempfile
 import time
 
 try:
-  import urllib2 as urllib
+  from urllib2 import HTTPError, URLError, urlopen
 except ImportError: # For Py3 compatibility
-  import urllib.request as urllib
-  import urllib.error as urllib
+  from urllib.error import HTTPError, URLError
+  from urllib.request import urlopen
 
 import zipfile
 
@@ -36,12 +37,13 @@ import zipfile
 # Do NOT CHANGE this if you don't know what you're doing -- see
 # https://chromium.googlesource.com/chromium/src/+/master/docs/updating_clang.md
 # Reverting problematic clang rolls is safe, though.
-CLANG_REVISION = '67510fac36d27b2e22c7cd955fc167136b737b93'
-CLANG_SVN_REVISION = '361212'
-CLANG_SUB_REVISION = 4
+CLANG_REVISION = 'f7e52fbdb5a7af8ea0808e98458b497125a5eca1'
+CLANG_SVN_REVISION = '365097'
+CLANG_SUB_REVISION = 8
 
 PACKAGE_VERSION = '%s-%s-%s' % (CLANG_SVN_REVISION, CLANG_REVISION[:8],
                                 CLANG_SUB_REVISION)
+# TODO(crbug.com/985289): Bump when rolling past r366427.
 RELEASE_VERSION = '9.0.0'
 
 
@@ -55,7 +57,7 @@ LLVM_BUILD_DIR = os.path.join(CHROMIUM_DIR, 'third_party', 'llvm-build',
                               'Release+Asserts')
 
 STAMP_FILE = os.path.normpath(
-    os.path.join(LLVM_BUILD_DIR, '..', 'cr_build_revision'))
+    os.path.join(LLVM_BUILD_DIR, 'cr_build_revision'))
 FORCE_HEAD_REVISION_FILE = os.path.normpath(os.path.join(LLVM_BUILD_DIR, '..',
                                                    'force_head_revision'))
 
@@ -99,8 +101,8 @@ def DownloadUrl(url, output_file):
     try:
       sys.stdout.write('Downloading %s ' % url)
       sys.stdout.flush()
-      response = urllib.urlopen(url)
-      total_size = int(response.info().getheader('Content-Length').strip())
+      response = urlopen(url)
+      total_size = int(response.info().get('Content-Length').strip())
       bytes_done = 0
       dots_printed = 0
       while True:
@@ -109,19 +111,19 @@ def DownloadUrl(url, output_file):
           break
         output_file.write(chunk)
         bytes_done += len(chunk)
-        num_dots = TOTAL_DOTS * bytes_done / total_size
+        num_dots = TOTAL_DOTS * bytes_done // total_size
         sys.stdout.write('.' * (num_dots - dots_printed))
         sys.stdout.flush()
         dots_printed = num_dots
       if bytes_done != total_size:
-        raise urllib.URLError("only got %d of %d bytes" %
-                              (bytes_done, total_size))
+        raise URLError("only got %d of %d bytes" %
+                       (bytes_done, total_size))
       print(' Done.')
       return
-    except urllib.URLError as e:
+    except URLError as e:
       sys.stdout.write('\n')
       print(e)
-      if num_retries == 0 or isinstance(e, urllib.HTTPError) and e.code == 404:
+      if num_retries == 0 or isinstance(e, HTTPError) and e.code == 404:
         raise e
       num_retries -= 1
       print('Retrying in %d s ...' % retry_wait_s)
@@ -171,7 +173,7 @@ def DownloadAndUnpackClangPackage(platform, output_dir, runtimes_only=False):
     if runtimes_only:
       path_prefix = 'lib/clang/' + RELEASE_VERSION + '/lib/'
     DownloadAndUnpack(cds_full_url, output_dir, path_prefix)
-  except urllib.URLError:
+  except URLError:
     print('Failed to download prebuilt clang %s' % cds_file)
     print('Use --force-local-build if you want to build locally.')
     print('Exiting.')
@@ -281,6 +283,11 @@ def main():
                       help='Verify that clang has the passed-in version.')
   args = parser.parse_args()
 
+  # TODO(crbug.com/985289): Remove when rolling past r366427.
+  if args.llvm_force_head_revision:
+    global RELEASE_VERSION
+    RELEASE_VERSION = '10.0.0'
+
   if args.force_local_build:
     print(('update.py --force-local-build is no longer used to build clang; '
            'use build.py instead.'))
diff --git a/chromium/tools/clang/stack_maps/OWNERS b/chromium/tools/clang/stack_maps/OWNERS
new file mode 100644
index 00000000000..2212c5146b3
--- /dev/null
+++ b/chromium/tools/clang/stack_maps/OWNERS
@@ -0,0 +1,4 @@
+mlippautz@chromium.org
+
+# TEAM: v8-dev@chromium.org
+# COMPONENT: Blink>JavaScript>GC
diff --git a/chromium/tools/clang/stack_maps/README b/chromium/tools/clang/stack_maps/README
new file mode 100644
index 00000000000..c7219f88f89
--- /dev/null
+++ b/chromium/tools/clang/stack_maps/README
@@ -0,0 +1,4 @@
+Prototype and playground for generating stack maps to garbage-collected objects
+using clang/llvm infrastructure.
+
+Design doc: https://bit.ly/chromium-stack-maps