Clean up forward declarations in Source/core/rendering

Source/core/rendering/RenderLayerModelObject.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010, 2012 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 10 matching lines @@
  */
 
 #ifndef RenderLayerModelObject_h
 #define RenderLayerModelObject_h
 
 #include "core/rendering/RenderObject.h"
 
 namespace blink {
 
 class RenderLayer;
-class CompositedLayerMapping;
 class ScrollableArea;
 
 enum LayerType {
     NoLayer,
     NormalLayer,
     // A forced or overflow clip layer is required for bookkeeping purposes,
     // but does not force a layer to be self painting.
     OverflowClipLayer,
     ForcedLayer
 };
@@ skipping 38 matching lines @@
 
     // Used to store state between styleWillChange and styleDidChange
     static bool s_wasFloating;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderLayerModelObject, isLayerModelObject());
 
 } // namespace blink
 
 #endif // RenderLayerModelObject_h