BASELINE: Update Chromium to 76.0.3809.94

Change-Id: I321c3f5f929c105aec0f98c5091ef6108822e647
Reviewed-by: Michael Brüning <michael.bruning@qt.io>

10 files changed, 381 insertions, 90 deletions

diff --git a/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.cc b/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.cc
index b86b3154914..9b449d37e38 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.cc
+++ b/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.cc
@@ -13,12 +13,17 @@ namespace blink {
 
 // static
 PortalHost* DOMWindowPortalHost::portalHost(LocalDOMWindow& window) {
+  if (ShouldExposePortalHost(window))
+    return &PortalHost::From(window);
+  return nullptr;
+}
+
+// static
+bool DOMWindowPortalHost::ShouldExposePortalHost(const LocalDOMWindow& window) {
   // The portal host is only exposed in the main frame of a page
   // embedded in a portal.
-  if (!window.GetFrame() || !window.GetFrame()->IsMainFrame() ||
-      !window.GetFrame()->GetPage()->InsidePortal())
-    return nullptr;
-  return &PortalHost::From(window);
+  return window.GetFrame() && window.GetFrame()->IsMainFrame() &&
+         window.GetFrame()->GetPage()->InsidePortal();
 }
 
 }  // namespace blink
diff --git a/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.h b/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.h
index 96e0154f385..87794ad6524 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.h
+++ b/chromium/third_party/blink/renderer/core/html/portal/dom_window_portal_host.h
@@ -15,6 +15,7 @@ class PortalHost;
 class CORE_EXPORT DOMWindowPortalHost {
  public:
   static PortalHost* portalHost(LocalDOMWindow& window);
+  static bool ShouldExposePortalHost(const LocalDOMWindow& window);
 };
 
 }  // namespace blink
diff --git a/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.cc b/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.cc
index ab3210d703e..bf97a2d4bd7 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.cc
+++ b/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.cc
@@ -6,6 +6,7 @@
 
 #include <utility>
 #include "services/service_manager/public/cpp/interface_provider.h"
+#include "third_party/blink/renderer/bindings/core/v8/script_event_listener.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
 #include "third_party/blink/renderer/bindings/core/v8/serialization/post_message_helper.h"
@@ -13,6 +14,8 @@
 #include "third_party/blink/renderer/core/dom/document.h"
 #include "third_party/blink/renderer/core/dom/dom_exception.h"
 #include "third_party/blink/renderer/core/dom/node.h"
+#include "third_party/blink/renderer/core/event_type_names.h"
+#include "third_party/blink/renderer/core/events/message_event.h"
 #include "third_party/blink/renderer/core/execution_context/execution_context.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
 #include "third_party/blink/renderer/core/frame/local_frame_client.h"
@@ -22,6 +25,7 @@
 #include "third_party/blink/renderer/core/html/parser/html_parser_idioms.h"
 #include "third_party/blink/renderer/core/html/portal/document_portals.h"
 #include "third_party/blink/renderer/core/html/portal/portal_activate_options.h"
+#include "third_party/blink/renderer/core/html/portal/portal_post_message_helper.h"
 #include "third_party/blink/renderer/core/html_names.h"
 #include "third_party/blink/renderer/core/inspector/console_message.h"
 #include "third_party/blink/renderer/core/inspector/thread_debugger.h"
@@ -30,7 +34,9 @@
 #include "third_party/blink/renderer/core/page/page.h"
 #include "third_party/blink/renderer/platform/bindings/script_state.h"
 #include "third_party/blink/renderer/platform/heap/handle.h"
+#include "third_party/blink/renderer/platform/heap/heap.h"
 #include "third_party/blink/renderer/platform/runtime_enabled_features.h"
+#include "third_party/blink/renderer/platform/weborigin/security_origin.h"
 #include "third_party/blink/renderer/platform/wtf/functional.h"
 
 namespace blink {
@@ -38,10 +44,12 @@ namespace blink {
 HTMLPortalElement::HTMLPortalElement(
     Document& document,
     const base::UnguessableToken& portal_token,
-    mojom::blink::PortalAssociatedPtr portal_ptr)
+    mojom::blink::PortalAssociatedPtr portal_ptr,
+    mojom::blink::PortalClientAssociatedRequest portal_client_request)
     : HTMLFrameOwnerElement(html_names::kPortalTag, document),
       portal_token_(portal_token),
-      portal_ptr_(std::move(portal_ptr)) {}
+      portal_ptr_(std::move(portal_ptr)),
+      portal_client_binding_(this, std::move(portal_client_request)) {}
 
 HTMLPortalElement::~HTMLPortalElement() {}
 
@@ -50,17 +58,20 @@ void HTMLPortalElement::Trace(Visitor* visitor) {
   visitor->Trace(portal_frame_);
 }
 
-HTMLElement* HTMLPortalElement::Create(Document& document) {
-  if (RuntimeEnabledFeatures::PortalsEnabled())
-    return MakeGarbageCollected<HTMLPortalElement>(document);
-  return HTMLUnknownElement::Create(html_names::kPortalTag, document);
-}
-
 void HTMLPortalElement::Navigate() {
   KURL url = GetNonEmptyURLAttribute(html_names::kSrcAttr);
-  if (!url.IsEmpty() && portal_ptr_) {
-    portal_ptr_->Navigate(url);
+  if (!portal_ptr_ || url.IsEmpty())
+    return;
+
+  if (!url.ProtocolIsInHTTPFamily()) {
+    GetDocument().AddConsoleMessage(ConsoleMessage::Create(
+        mojom::ConsoleMessageSource::kRendering,
+        mojom::ConsoleMessageLevel::kWarning,
+        "Portals only allow navigation to protocols in the HTTP family."));
+    return;
   }
+
+  portal_ptr_->Navigate(url);
 }
 
 void HTMLPortalElement::ConsumePortal() {
@@ -69,6 +80,7 @@ void HTMLPortalElement::ConsumePortal() {
     portal_token_ = base::UnguessableToken();
   }
   portal_ptr_.reset();
+  portal_client_binding_.Close();
 }
 
 namespace {
@@ -124,42 +136,6 @@ BlinkTransferableMessage ActivateDataAsMessage(
   return msg;
 }
 
-BlinkTransferableMessage CreateMessageForPostMessage(
-    ScriptState* script_state,
-    const ScriptValue& message,
-    const WindowPostMessageOptions* options,
-    ExceptionState& exception_state) {
-  BlinkTransferableMessage transferable_message;
-  Transferables transferables;
-  scoped_refptr<SerializedScriptValue> serialized_message =
-      PostMessageHelper::SerializeMessageByMove(script_state->GetIsolate(),
-                                                message, options, transferables,
-                                                exception_state);
-  if (exception_state.HadException())
-    return {};
-  DCHECK(serialized_message);
-  transferable_message.message = serialized_message;
-
-  // Disentangle the port in preparation for sending it to the remote context.
-  auto* execution_context = ExecutionContext::From(script_state);
-  transferable_message.ports = MessagePort::DisentanglePorts(
-      execution_context, transferables.message_ports, exception_state);
-  if (exception_state.HadException())
-    return {};
-
-  if (ThreadDebugger* debugger =
-          ThreadDebugger::From(script_state->GetIsolate())) {
-    transferable_message.sender_stack_trace_id =
-        debugger->StoreCurrentStackTrace("postMessage");
-  }
-
-  transferable_message.user_activation =
-      PostMessageHelper::CreateUserActivationSnapshot(execution_context,
-                                                      options);
-
-  return transferable_message;
-}
-
 }  // namespace
 
 ScriptPromise HTMLPortalElement::activate(ScriptState* script_state,
@@ -254,18 +230,55 @@ void HTMLPortalElement::postMessage(ScriptState* script_state,
     return;
   }
 
-  scoped_refptr<const SecurityOrigin> target_origin = nullptr;
-  if (options->targetOrigin() == "/")
-    target_origin = GetDocument().GetSecurityOrigin();
-  else if (options->targetOrigin() != "*")
-    target_origin = SecurityOrigin::CreateFromString(options->targetOrigin());
+  scoped_refptr<const SecurityOrigin> target_origin =
+      PostMessageHelper::GetTargetOrigin(options, GetDocument(),
+                                         exception_state);
+  if (exception_state.HadException())
+    return;
 
-  BlinkTransferableMessage transferable_message = CreateMessageForPostMessage(
-      script_state, message, options, exception_state);
+  BlinkTransferableMessage transferable_message =
+      PortalPostMessageHelper::CreateMessage(script_state, message, options,
+                                             exception_state);
   if (exception_state.HadException())
     return;
 
-  portal_ptr_->PostMessage(std::move(transferable_message), target_origin);
+  portal_ptr_->PostMessageToGuest(std::move(transferable_message),
+                                  target_origin);
+}
+
+EventListener* HTMLPortalElement::onmessage() {
+  return GetAttributeEventListener(event_type_names::kMessage);
+}
+
+void HTMLPortalElement::setOnmessage(EventListener* listener) {
+  SetAttributeEventListener(event_type_names::kMessage, listener);
+}
+
+EventListener* HTMLPortalElement::onmessageerror() {
+  return GetAttributeEventListener(event_type_names::kMessageerror);
+}
+
+void HTMLPortalElement::setOnmessageerror(EventListener* listener) {
+  SetAttributeEventListener(event_type_names::kMessageerror, listener);
+}
+
+void HTMLPortalElement::ForwardMessageFromGuest(
+    BlinkTransferableMessage message,
+    const scoped_refptr<const SecurityOrigin>& source_origin,
+    const scoped_refptr<const SecurityOrigin>& target_origin) {
+  if (!portal_ptr_)
+    return;
+
+  PortalPostMessageHelper::CreateAndDispatchMessageEvent(
+      this, std::move(message), source_origin, target_origin);
+}
+
+void HTMLPortalElement::DispatchLoadEvent() {
+  if (!portal_ptr_)
+    return;
+
+  DispatchLoad();
+  GetDocument().CheckCompleted();
 }
 
 HTMLPortalElement::InsertionNotificationRequest HTMLPortalElement::InsertedInto(
@@ -293,9 +306,11 @@ HTMLPortalElement::InsertionNotificationRequest HTMLPortalElement::InsertedInto(
         WTF::Bind(&HTMLPortalElement::ConsumePortal, WrapWeakPersistent(this)));
     DocumentPortals::From(GetDocument()).OnPortalInserted(this);
   } else {
+    mojom::blink::PortalClientAssociatedPtr client;
+    portal_client_binding_.Bind(mojo::MakeRequest(&client));
     std::tie(portal_frame_, portal_token_) =
         GetDocument().GetFrame()->Client()->CreatePortal(
-            this, mojo::MakeRequest(&portal_ptr_));
+            this, mojo::MakeRequest(&portal_ptr_), client.PassInterface());
     portal_ptr_.set_connection_error_handler(
         WTF::Bind(&HTMLPortalElement::ConsumePortal, WrapWeakPersistent(this)));
     DocumentPortals::From(GetDocument()).OnPortalInserted(this);
@@ -324,8 +339,26 @@ void HTMLPortalElement::ParseAttribute(
     const AttributeModificationParams& params) {
   HTMLFrameOwnerElement::ParseAttribute(params);
 
-  if (params.name == html_names::kSrcAttr)
+  if (params.name == html_names::kSrcAttr) {
     Navigate();
+    return;
+  }
+
+  struct {
+    const QualifiedName& name;
+    const AtomicString& event_name;
+  } event_handler_attributes[] = {
+      {html_names::kOnmessageAttr, event_type_names::kMessage},
+      {html_names::kOnmessageerrorAttr, event_type_names::kMessageerror},
+  };
+  for (const auto& attribute : event_handler_attributes) {
+    if (params.name == attribute.name) {
+      SetAttributeEventListener(
+          attribute.event_name,
+          CreateAttributeEventListener(this, attribute.name, params.new_value));
+      return;
+    }
+  }
 }
 
 LayoutObject* HTMLPortalElement::CreateLayoutObject(const ComputedStyle& style,
diff --git a/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.h b/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.h
index 331fd841e6e..296f102267d 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.h
+++ b/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.h
@@ -6,6 +6,7 @@
 #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PORTAL_HTML_PORTAL_ELEMENT_H_
 
 #include "base/unguessable_token.h"
+#include "mojo/public/cpp/bindings/associated_binding.h"
 #include "third_party/blink/public/mojom/portal/portal.mojom-blink.h"
 #include "third_party/blink/renderer/bindings/core/v8/script_promise.h"
 #include "third_party/blink/renderer/core/core_export.h"
@@ -24,16 +25,17 @@ class ScriptState;
 // activated using script. The portal element is still under development and not
 // part of the HTML standard. It can be enabled by passing
 // --enable-features=Portals. See also https://github.com/WICG/portals.
-class CORE_EXPORT HTMLPortalElement : public HTMLFrameOwnerElement {
+class CORE_EXPORT HTMLPortalElement : public HTMLFrameOwnerElement,
+                                      public mojom::blink::PortalClient {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
-  static HTMLElement* Create(Document&);
-
   explicit HTMLPortalElement(
       Document& document,
       const base::UnguessableToken& portal_token = base::UnguessableToken(),
-      mojom::blink::PortalAssociatedPtr portal_ptr = nullptr);
+      mojom::blink::PortalAssociatedPtr portal_ptr = nullptr,
+      mojom::blink::PortalClientAssociatedRequest portal_client_request =
+          nullptr);
   ~HTMLPortalElement() override;
 
   // ScriptWrappable overrides.
@@ -50,6 +52,17 @@ class CORE_EXPORT HTMLPortalElement : public HTMLFrameOwnerElement {
                    const ScriptValue& message,
                    const WindowPostMessageOptions* options,
                    ExceptionState& exception_state);
+  EventListener* onmessage();
+  void setOnmessage(EventListener* listener);
+  EventListener* onmessageerror();
+  void setOnmessageerror(EventListener* listener);
+
+  // blink::mojom::PortalClient implementation
+  void ForwardMessageFromGuest(
+      BlinkTransferableMessage message,
+      const scoped_refptr<const SecurityOrigin>& source_origin,
+      const scoped_refptr<const SecurityOrigin>& target_origin) override;
+  void DispatchLoadEvent() override;
 
   const base::UnguessableToken& GetToken() const { return portal_token_; }
 
@@ -94,6 +107,7 @@ class CORE_EXPORT HTMLPortalElement : public HTMLFrameOwnerElement {
   bool is_activating_ = false;
 
   mojom::blink::PortalAssociatedPtr portal_ptr_;
+  mojo::AssociatedBinding<mojom::blink::PortalClient> portal_client_binding_;
 };
 
 }  // namespace blink
diff --git a/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.idl b/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.idl
index e0b1eae11e4..cb1b02fc1ff 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.idl
+++ b/chromium/third_party/blink/renderer/core/html/portal/html_portal_element.idl
@@ -11,4 +11,7 @@ interface HTMLPortalElement : HTMLElement {
   [CallWith=ScriptState, RaisesException] void postMessage(any message, DOMString targetOrigin,
                                      optional sequence<object> transfer = []);
   [CallWith=ScriptState, RaisesException] void postMessage(any message, optional WindowPostMessageOptions options);
+
+  attribute EventHandler onmessage;
+  attribute EventHandler onmessageerror;
 };
diff --git a/chromium/third_party/blink/renderer/core/html/portal/portal_host.cc b/chromium/third_party/blink/renderer/core/html/portal/portal_host.cc
index 1dc6169b02a..0754209ec3c 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/portal_host.cc
+++ b/chromium/third_party/blink/renderer/core/html/portal/portal_host.cc
@@ -4,12 +4,17 @@
 
 #include "third_party/blink/renderer/core/html/portal/portal_host.h"
 
+#include <utility>
+#include "third_party/blink/public/common/associated_interfaces/associated_interface_provider.h"
+#include "third_party/blink/renderer/bindings/core/v8/script_value.h"
+#include "third_party/blink/renderer/bindings/core/v8/serialization/post_message_helper.h"
 #include "third_party/blink/renderer/core/dom/document.h"
-#include "third_party/blink/renderer/core/events/message_event.h"
 #include "third_party/blink/renderer/core/execution_context/execution_context.h"
 #include "third_party/blink/renderer/core/frame/local_dom_window.h"
-#include "third_party/blink/renderer/core/frame/user_activation.h"
-#include "third_party/blink/renderer/core/inspector/main_thread_debugger.h"
+#include "third_party/blink/renderer/core/frame/local_frame_client.h"
+#include "third_party/blink/renderer/core/frame/window_post_message_options.h"
+#include "third_party/blink/renderer/core/html/portal/dom_window_portal_host.h"
+#include "third_party/blink/renderer/core/html/portal/portal_post_message_helper.h"
 #include "third_party/blink/renderer/core/page/page.h"
 #include "third_party/blink/renderer/platform/wtf/text/atomic_string.h"
 
@@ -49,34 +54,87 @@ PortalHost* PortalHost::ToPortalHost() {
   return this;
 }
 
+Document* PortalHost::GetDocument() const {
+  return To<Document>(GetExecutionContext());
+}
+
+void PortalHost::OnPortalActivated() {
+  portal_host_ptr_.reset();
+}
+
+void PortalHost::postMessage(ScriptState* script_state,
+                             const ScriptValue& message,
+                             const String& target_origin,
+                             Vector<ScriptValue>& transfer,
+                             ExceptionState& exception_state) {
+  WindowPostMessageOptions* options = WindowPostMessageOptions::Create();
+  options->setTargetOrigin(target_origin);
+  if (!transfer.IsEmpty())
+    options->setTransfer(transfer);
+  postMessage(script_state, message, options, exception_state);
+}
+
+void PortalHost::postMessage(ScriptState* script_state,
+                             const ScriptValue& message,
+                             const WindowPostMessageOptions* options,
+                             ExceptionState& exception_state) {
+  if (!DOMWindowPortalHost::ShouldExposePortalHost(*GetSupplementable())) {
+    exception_state.ThrowDOMException(
+        DOMExceptionCode::kInvalidStateError,
+        "The document is no longer inside a portal");
+    return;
+  }
+
+  scoped_refptr<const SecurityOrigin> target_origin =
+      PostMessageHelper::GetTargetOrigin(options, *GetDocument(),
+                                         exception_state);
+  if (exception_state.HadException())
+    return;
+
+  BlinkTransferableMessage transferable_message =
+      PortalPostMessageHelper::CreateMessage(script_state, message, options,
+                                             exception_state);
+  if (exception_state.HadException())
+    return;
+
+  GetPortalHostInterface().PostMessageToHost(std::move(transferable_message),
+                                             target_origin);
+}
+
+EventListener* PortalHost::onmessage() {
+  return GetAttributeEventListener(event_type_names::kMessage);
+}
+
+void PortalHost::setOnmessage(EventListener* listener) {
+  SetAttributeEventListener(event_type_names::kMessage, listener);
+}
+
+EventListener* PortalHost::onmessageerror() {
+  return GetAttributeEventListener(event_type_names::kMessageerror);
+}
+
+void PortalHost::setOnmessageerror(EventListener* listener) {
+  SetAttributeEventListener(event_type_names::kMessageerror, listener);
+}
+
 void PortalHost::ReceiveMessage(
     BlinkTransferableMessage message,
     scoped_refptr<const SecurityOrigin> source_origin,
     scoped_refptr<const SecurityOrigin> target_origin) {
-  DCHECK(GetSupplementable()->document()->GetPage()->InsidePortal());
-  if (target_origin && !target_origin->IsSameSchemeHostPort(
-                           GetExecutionContext()->GetSecurityOrigin())) {
-    return;
-  }
+  DCHECK(GetDocument()->GetPage()->InsidePortal());
+  PortalPostMessageHelper::CreateAndDispatchMessageEvent(
+      this, std::move(message), source_origin, target_origin);
+}
 
-  UserActivation* user_activation = nullptr;
-  if (message.user_activation) {
-    user_activation = MakeGarbageCollected<UserActivation>(
-        message.user_activation->has_been_active,
-        message.user_activation->was_active);
+mojom::blink::PortalHost& PortalHost::GetPortalHostInterface() {
+  if (!portal_host_ptr_) {
+    DCHECK(GetDocument()->GetFrame());
+    GetDocument()
+        ->GetFrame()
+        ->GetRemoteNavigationAssociatedInterfaces()
+        ->GetInterface(&portal_host_ptr_);
   }
-
-  MessageEvent* event = MessageEvent::Create(message.ports, message.message,
-                                             source_origin->ToString(),
-                                             String(), this, user_activation);
-  event->EntangleMessagePorts(GetExecutionContext());
-
-  ThreadDebugger* debugger = MainThreadDebugger::Instance();
-  if (debugger)
-    debugger->ExternalAsyncTaskStarted(message.sender_stack_trace_id);
-  DispatchEvent(*event);
-  if (debugger)
-    debugger->ExternalAsyncTaskFinished(message.sender_stack_trace_id);
+  return *portal_host_ptr_;
 }
 
 }  // namespace blink
diff --git a/chromium/third_party/blink/renderer/core/html/portal/portal_host.h b/chromium/third_party/blink/renderer/core/html/portal/portal_host.h
index 1ba227fbda7..9fa6c67e828 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/portal_host.h
+++ b/chromium/third_party/blink/renderer/core/html/portal/portal_host.h
@@ -5,6 +5,7 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PORTAL_PORTAL_HOST_H_
 #define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PORTAL_PORTAL_HOST_H_
 
+#include "third_party/blink/public/mojom/portal/portal.mojom-blink.h"
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/dom/events/event_target.h"
 #include "third_party/blink/renderer/core/messaging/blink_transferable_message.h"
@@ -12,9 +13,12 @@
 
 namespace blink {
 
+class Document;
 class ExecutionContext;
 class LocalDOMWindow;
+class ScriptValue;
 class SecurityOrigin;
+class WindowPostMessageOptions;
 
 class CORE_EXPORT PortalHost : public EventTargetWithInlineData,
                                public Supplement<LocalDOMWindow> {
@@ -34,9 +38,34 @@ class CORE_EXPORT PortalHost : public EventTargetWithInlineData,
   ExecutionContext* GetExecutionContext() const override;
   PortalHost* ToPortalHost() override;
 
+  Document* GetDocument() const;
+
+  // Called immediately before dispatching the onactivate event.
+  void OnPortalActivated();
+
+  // idl implementation
+  void postMessage(ScriptState* script_state,
+                   const ScriptValue& message,
+                   const String& target_origin,
+                   Vector<ScriptValue>& transfer,
+                   ExceptionState& exception_state);
+  void postMessage(ScriptState* script_state,
+                   const ScriptValue& message,
+                   const WindowPostMessageOptions* options,
+                   ExceptionState& exception_state);
+  EventListener* onmessage();
+  void setOnmessage(EventListener* listener);
+  EventListener* onmessageerror();
+  void setOnmessageerror(EventListener* listener);
+
   void ReceiveMessage(BlinkTransferableMessage message,
                       scoped_refptr<const SecurityOrigin> source_origin,
                       scoped_refptr<const SecurityOrigin> target_origin);
+
+ private:
+  mojom::blink::PortalHost& GetPortalHostInterface();
+
+  mojom::blink::PortalHostAssociatedPtr portal_host_ptr_;
 };
 
 }  // namespace blink
diff --git a/chromium/third_party/blink/renderer/core/html/portal/portal_host.idl b/chromium/third_party/blink/renderer/core/html/portal/portal_host.idl
index 2cf404856c1..ced86df51f9 100644
--- a/chromium/third_party/blink/renderer/core/html/portal/portal_host.idl
+++ b/chromium/third_party/blink/renderer/core/html/portal/portal_host.idl
@@ -5,4 +5,12 @@
 // https://wicg.github.io/portals/#the-portalhost-interface
 
 [Exposed=Window, RuntimeEnabled=Portals]
-interface PortalHost : EventTarget {};
+interface PortalHost : EventTarget {
+  [RaisesException, CallWith=ScriptState] void postMessage(any message, DOMString targetOrigin,
+                                                           optional sequence<object> transfer = []);
+  [RaisesException, CallWith=ScriptState] void postMessage(any message,
+                                                           optional WindowPostMessageOptions options);
+
+  attribute EventHandler onmessage;
+  attribute EventHandler onmessageerror;
+};
diff --git a/chromium/third_party/blink/renderer/core/html/portal/portal_post_message_helper.cc b/chromium/third_party/blink/renderer/core/html/portal/portal_post_message_helper.cc
new file mode 100644
index 00000000000..82e04cc752c
--- /dev/null
+++ b/chromium/third_party/blink/renderer/core/html/portal/portal_post_message_helper.cc
@@ -0,0 +1,99 @@
+// Copyright 2019 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 "third_party/blink/renderer/core/html/portal/portal_post_message_helper.h"
+
+#include "third_party/blink/renderer/bindings/core/v8/serialization/post_message_helper.h"
+#include "third_party/blink/renderer/bindings/core/v8/serialization/serialized_script_value.h"
+#include "third_party/blink/renderer/bindings/core/v8/serialization/transferables.h"
+#include "third_party/blink/renderer/core/dom/events/event_target.h"
+#include "third_party/blink/renderer/core/events/message_event.h"
+#include "third_party/blink/renderer/core/execution_context/execution_context.h"
+#include "third_party/blink/renderer/core/frame/user_activation.h"
+#include "third_party/blink/renderer/core/frame/window_post_message_options.h"
+#include "third_party/blink/renderer/core/html/portal/html_portal_element.h"
+#include "third_party/blink/renderer/core/inspector/main_thread_debugger.h"
+#include "third_party/blink/renderer/core/inspector/thread_debugger.h"
+#include "third_party/blink/renderer/core/messaging/blink_transferable_message.h"
+#include "third_party/blink/renderer/core/messaging/message_port.h"
+#include "third_party/blink/renderer/platform/bindings/exception_state.h"
+#include "third_party/blink/renderer/platform/bindings/script_state.h"
+#include "third_party/blink/renderer/platform/weborigin/security_origin.h"
+
+namespace blink {
+
+// static
+BlinkTransferableMessage PortalPostMessageHelper::CreateMessage(
+    ScriptState* script_state,
+    const ScriptValue& message,
+    const WindowPostMessageOptions* options,
+    ExceptionState& exception_state) {
+  BlinkTransferableMessage transferable_message;
+  Transferables transferables;
+  scoped_refptr<SerializedScriptValue> serialized_message =
+      PostMessageHelper::SerializeMessageByMove(script_state->GetIsolate(),
+                                                message, options, transferables,
+                                                exception_state);
+  if (exception_state.HadException())
+    return {};
+  DCHECK(serialized_message);
+  transferable_message.message = serialized_message;
+
+  // Disentangle the port in preparation for sending it to the remote context.
+  auto* execution_context = ExecutionContext::From(script_state);
+  transferable_message.ports = MessagePort::DisentanglePorts(
+      execution_context, transferables.message_ports, exception_state);
+  if (exception_state.HadException())
+    return {};
+
+  if (ThreadDebugger* debugger =
+          ThreadDebugger::From(script_state->GetIsolate())) {
+    transferable_message.sender_stack_trace_id =
+        debugger->StoreCurrentStackTrace("postMessage");
+  }
+
+  transferable_message.user_activation =
+      PostMessageHelper::CreateUserActivationSnapshot(execution_context,
+                                                      options);
+
+  return transferable_message;
+}
+
+// static
+void PortalPostMessageHelper::CreateAndDispatchMessageEvent(
+    EventTarget* event_target,
+    BlinkTransferableMessage message,
+    scoped_refptr<const SecurityOrigin> source_origin,
+    scoped_refptr<const SecurityOrigin> target_origin) {
+  DCHECK(event_target->ToPortalHost() ||
+         (event_target->ToNode() &&
+          ToHTMLPortalElementOrNull(event_target->ToNode())));
+
+  if (target_origin &&
+      !target_origin->IsSameSchemeHostPort(
+          event_target->GetExecutionContext()->GetSecurityOrigin())) {
+    return;
+  }
+
+  UserActivation* user_activation = nullptr;
+  if (message.user_activation) {
+    user_activation = MakeGarbageCollected<UserActivation>(
+        message.user_activation->has_been_active,
+        message.user_activation->was_active);
+  }
+
+  MessageEvent* event = MessageEvent::Create(
+      message.ports, message.message, source_origin->ToString(), String(),
+      event_target, user_activation);
+  event->EntangleMessagePorts(event_target->GetExecutionContext());
+
+  ThreadDebugger* debugger = MainThreadDebugger::Instance();
+  if (debugger)
+    debugger->ExternalAsyncTaskStarted(message.sender_stack_trace_id);
+  event_target->DispatchEvent(*event);
+  if (debugger)
+    debugger->ExternalAsyncTaskFinished(message.sender_stack_trace_id);
+}
+
+}  // namespace blink
diff --git a/chromium/third_party/blink/renderer/core/html/portal/portal_post_message_helper.h b/chromium/third_party/blink/renderer/core/html/portal/portal_post_message_helper.h
new file mode 100644
index 00000000000..8a6a24782f5
--- /dev/null
+++ b/chromium/third_party/blink/renderer/core/html/portal/portal_post_message_helper.h
@@ -0,0 +1,41 @@
+// Copyright 2019 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 THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PORTAL_PORTAL_POST_MESSAGE_HELPER_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PORTAL_PORTAL_POST_MESSAGE_HELPER_H_
+
+#include "base/memory/scoped_refptr.h"
+#include "third_party/blink/renderer/core/core_export.h"
+#include "third_party/blink/renderer/platform/wtf/allocator.h"
+
+namespace blink {
+
+class EventTarget;
+class ExceptionState;
+class ScriptState;
+class ScriptValue;
+class SecurityOrigin;
+class WindowPostMessageOptions;
+struct BlinkTransferableMessage;
+
+class CORE_EXPORT PortalPostMessageHelper {
+  STATIC_ONLY(PortalPostMessageHelper);
+
+ public:
+  static BlinkTransferableMessage CreateMessage(
+      ScriptState* script_state,
+      const ScriptValue& message,
+      const WindowPostMessageOptions* options,
+      ExceptionState& exception_state);
+
+  static void CreateAndDispatchMessageEvent(
+      EventTarget* target,
+      BlinkTransferableMessage message,
+      scoped_refptr<const SecurityOrigin> source_origin,
+      scoped_refptr<const SecurityOrigin> target_origin);
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_PORTAL_PORTAL_POST_MESSAGE_HELPER_H_