Clean forward declaration in public

public/platform/WebExternalTextureLayer.h

 /*
  * Copyright (C) 2011 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 14 matching lines @@
 
 #ifndef WebExternalTextureLayer_h
 #define WebExternalTextureLayer_h
 
 #include "WebCommon.h"
 #include "WebFloatRect.h"
 #include "WebLayer.h"
 
 namespace blink {
 
-class WebExternalTextureLayerClient;
-
 // This class represents a layer that renders a texture that is generated
 // externally (not managed by the WebLayerTreeView).
 // The texture will be used by the WebLayerTreeView during compositing passes.
 // When in single-thread mode, this means during WebLayerTreeView::composite().
 // When using the threaded compositor, this can mean at an arbitrary time until
 // the WebLayerTreeView is destroyed.
 class WebExternalTextureLayer {
 public:
     virtual ~WebExternalTextureLayer() { }
 
@@ skipping 13 matching lines @@
     virtual void setBlendBackgroundColor(bool) = 0;
 
     // Sets whether this context should be rate limited by the compositor. Rate limiting works by blocking
     // invalidate() and invalidateRect() calls if the compositor is too many frames behind.
     virtual void setRateLimitContext(bool) = 0;
 };
 
 } // namespace blink
 
 #endif // WebExternalTextureLayer_h