Reland of Messaging: Avoid calling non-thread-safe functions in MessagePort::messageAvailable()

third_party/WebKit/Source/core/dom/MessagePort.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 16 matching lines @@
 #ifndef MessagePort_h
 #define MessagePort_h
 
 #include <memory>
 #include "bindings/core/v8/ActiveScriptWrappable.h"
 #include "bindings/core/v8/SerializedScriptValue.h"
 #include "core/CoreExport.h"
 #include "core/dom/ContextLifecycleObserver.h"
 #include "core/events/EventListener.h"
 #include "core/events/EventTarget.h"
+#include "platform/WebTaskRunner.h"
 #include "platform/wtf/PassRefPtr.h"
 #include "platform/wtf/RefPtr.h"
 #include "platform/wtf/Vector.h"
 #include "public/platform/WebMessagePortChannel.h"
 #include "public/platform/WebMessagePortChannelClient.h"
 
 namespace blink {
 
 class ExceptionState;
 class ExecutionContext;
@@ skipping 86 matching lines @@
   bool TryGetMessage(RefPtr<SerializedScriptValue>& message,
                      MessagePortChannelArray& channels);
 
  private:
   // WebMessagePortChannelClient implementation.
   void MessageAvailable() override;
   void DispatchMessages();
 
   std::unique_ptr<WebMessagePortChannel> entangled_channel_;
 
-  int pending_dispatch_task_;
-  bool started_;
-  bool closed_;
+  int pending_dispatch_task_ = 0;
+  bool started_ = false;
+  bool closed_ = false;
+
+  RefPtr<WebTaskRunner> task_runner_;
 };
 
 }  // namespace blink
 
 #endif  // MessagePort_h