ServiceWorker: Introduce ServiceWorkerMessageEvent to replace MessageEvent (1/3).

public/platform/WebServiceWorkerProviderClient.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 29 matching lines @@
 class WebString;
 
 // This class is the interface for embedders to talk to
 // ServiceWorkerContainer.
 class BLINK_PLATFORM_EXPORT WebServiceWorkerProviderClient {
 public:
     virtual ~WebServiceWorkerProviderClient() { }
 
     virtual void setController(WebServiceWorker*, bool shouldNotifyControllerChange) = 0;
 
+    // FIXME: Remove this when Chrome side CL landed.
     virtual void dispatchMessageEvent(const WebString& message, const WebMessagePortChannelArray&) = 0;
+    virtual void dispatchMessageEvent(WebServiceWorker*, const WebString& message, const WebMessagePortChannelArray& channels)
+    {
+        return dispatchMessageEvent(message, channels);
+    }
 };
 
 } // namespace blink
 
 #endif // WebServiceWorkerProviderClient_h