Clean forward declaration in public

public/platform/WebExternalTextureLayerClient.h

 /*
  * Copyright (C) 2012 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:
  *
  * 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
@@ skipping 13 matching lines @@
  */
 
 #ifndef WebExternalTextureLayerClient_h
 #define WebExternalTextureLayerClient_h
 
 #include "WebCommon.h"
 #include "WebSize.h"
 
 namespace blink {
 
-class WebGraphicsContext3D;
 class WebExternalBitmap;
 struct WebExternalTextureMailbox;
 
 class BLINK_PLATFORM_EXPORT WebExternalTextureLayerClient {
 public:
     // Returns true and provides a mailbox if a new frame is available. If the WebExternalBitmap
     // isn't 0, then it should also be filled in with the contents of this frame.
     // Returns false if no new data is available and the old mailbox and bitmap are to be reused.
     virtual bool prepareMailbox(WebExternalTextureMailbox*, WebExternalBitmap* = 0) = 0;
 
     // Notifies the client when a mailbox is no longer in use by the compositor and provides
     // a sync point to wait on before the mailbox could be consumes again by the client. The
     // boolean flag indicates if the mailbox resource is treated as lost by client.
     virtual void mailboxReleased(const WebExternalTextureMailbox&, bool lostResource) = 0;
 
 protected:
     virtual ~WebExternalTextureLayerClient() { }
 };
 
 } // namespace blink
 
 #endif // WebExternalTextureLayerClient_h