Reland again "Decode GIF image frames on demand".

Source/core/svg/graphics/SVGImageForContainer.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:
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 52 matching lines @@
     virtual PassNativeImagePtr nativeImageForCurrentFrame() OVERRIDE;
 
 private:
     SVGImageForContainer(SVGImage* image, const FloatSize& containerSize, float zoom)
         : m_image(image)
         , m_containerSize(containerSize)
         , m_zoom(zoom)
     {
     }
 
-    virtual void destroyDecodedData(bool /*destroyAll*/ = true) { }
-    virtual unsigned decodedSize() const { return 0; }
+    virtual void destroyDecodedData() OVERRIDE { }
+    virtual unsigned decodedSize() const OVERRIDE { return 0; }
 
     SVGImage* m_image;
     const FloatSize m_containerSize;
     const float m_zoom;
 };
 }
 
 #endif // SVGImageForContainer_h