Clean up forward declarations in Source/platform

Source/platform/graphics/Canvas2DImageBufferSurface.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 16 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef Canvas2DImageBufferSurface_h
 #define Canvas2DImageBufferSurface_h
 
 #include "platform/graphics/Canvas2DLayerBridge.h"
 #include "platform/graphics/ImageBufferSurface.h"
 
-class SkImage;
-
 namespace blink {
 
 // This shim necessary because ImageBufferSurfaces are not allowed to be RefCounted
 class Canvas2DImageBufferSurface final : public ImageBufferSurface {
 public:
     Canvas2DImageBufferSurface(const IntSize& size, OpacityMode opacityMode = NonOpaque, int msaaSampleCount = 1)
         : ImageBufferSurface(size, opacityMode)
         , m_layerBridge(Canvas2DLayerBridge::create(size, opacityMode, msaaSampleCount))
     {
         clear();
@@ skipping 18 matching lines @@
     virtual void setImageBuffer(ImageBuffer* imageBuffer) override { m_layerBridge->setImageBuffer(imageBuffer); }
 
     virtual PassRefPtr<SkImage> newImageSnapshot() const override { return m_layerBridge->newImageSnapshot(); }
 private:
     RefPtr<Canvas2DLayerBridge> m_layerBridge;
 };
 
 } // namespace blink
 
 #endif