Oilpan: Reduce RefPtr to WorkerGlobalScope.

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 46 matching lines @@
 typedef Vector<OwnPtr<blink::WebMessagePortChannel>, 1> MessagePortChannelArray;
 
 class MessagePort FINAL : public RefCountedWillBeRefCountedGarbageCollected<MessagePort>
     , public ActiveDOMObject
     , public EventTargetWithInlineData
     , public ScriptWrappable
     , public blink::WebMessagePortChannelClient {
     REFCOUNTED_EVENT_TARGET(MessagePort);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(MessagePort);
 public:
-    static PassRefPtr<MessagePort> create(ExecutionContext&);
+    static PassRefPtrWillBeRawPtr<MessagePort> create(ExecutionContext&);
     virtual ~MessagePort();
 
     void postMessage(PassRefPtr<SerializedScriptValue> message, const MessagePortArray*, ExceptionState&);
 
     void start();
     void close();
 
     void entangle(PassOwnPtr<blink::WebMessagePortChannel>);
     PassOwnPtr<blink::WebMessagePortChannel> disentangle();
 
@@ skipping 40 matching lines @@
 
     bool m_started;
     bool m_closed;
 
     WeakPtrFactory<MessagePort> m_weakFactory;
 };
 
 } // namespace WebCore
 
 #endif // MessagePort_h