Set MessageEvent.source to the newly created port for shared workers' connect events

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 57 matching lines @@
     // Returns 0 if the passed array is 0/empty.
     static PassOwnPtr<MessagePortArray> entanglePorts(ScriptExecutionContext&, PassOwnPtr<MessagePortChannelArray>);
 
     void messageAvailable();
     bool started() const { return m_started; }
 
     void contextDestroyed();
 
     virtual const AtomicString& interfaceName() const OVERRIDE;
     virtual ScriptExecutionContext* scriptExecutionContext() const OVERRIDE;
+    MessagePort* toMessagePort() OVERRIDE { return this; }
 
     void dispatchMessages();
 
     using RefCounted<MessagePort>::ref;
     using RefCounted<MessagePort>::deref;
 
     bool hasPendingActivity();
 
     void setOnmessage(PassRefPtr<EventListener> listener, DOMWrapperWorld* world)
     {
@@ skipping 26 matching lines @@
     bool m_started;
     bool m_closed;
 
     ScriptExecutionContext* m_scriptExecutionContext;
     EventTargetData m_eventTargetData;
 };
 
 } // namespace WebCore
 
 #endif // MessagePort_h