Have MessagePort use Oilpan-based weak pointers.

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 22 matching lines @@
 #include "core/dom/ActiveDOMObject.h"
 #include "core/events/EventListener.h"
 #include "core/events/EventTarget.h"
 #include "public/platform/WebMessagePortChannel.h"
 #include "public/platform/WebMessagePortChannelClient.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
-#include "wtf/WeakPtr.h"
 
 namespace blink {
 
 class ExceptionState;
 class ExecutionContext;
 class MessagePort;
 class ScriptState;
 class SerializedScriptValue;
 
 // Not to be confused with WebMessagePortChannelArray; this one uses Vector and OwnPtr instead of WebVector and raw pointers.
@@ skipping 61 matching lines @@
     explicit MessagePort(ExecutionContext&);
     bool tryGetMessage(RefPtr<SerializedScriptValue>& message, OwnPtr<MessagePortChannelArray>& channels);
 
 private:
     // WebMessagePortChannelClient implementation.
     void messageAvailable() override;
     v8::Isolate* scriptIsolate() override;
     v8::Local<v8::Context> scriptContextForMessageConversion() override;
     void dispatchMessages();
 
     OwnPtr<WebMessagePortChannel> m_entangledChannel;

[sof, 2016/04/27 13:50:36]

Note: I'm considering making MessagePort eagerly finalized independently of this
WeakPtr<> issue -- the current delayed close()ing looks shaky.

 
     bool m_started;
     bool m_closed;
 
-    WeakPtrFactory<MessagePort> m_weakFactory;
-
     RefPtr<ScriptState> m_scriptStateForConversion;
 };
 
 } // namespace blink
 
 #endif // MessagePort_h