Add animation support for WebP images

Source/core/platform/image-decoders/gif/GIFImageDecoder.h

 /*
  * Copyright (C) 2006 Apple Computer, 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 32 matching lines @@
 
         // ImageDecoder
         virtual String filenameExtension() const OVERRIDE { return "gif"; }
         virtual void setData(SharedBuffer* data, bool allDataReceived) OVERRIDE;
         virtual bool isSizeAvailable() OVERRIDE;
         virtual size_t frameCount() OVERRIDE;
         virtual int repetitionCount() const OVERRIDE;
         virtual ImageFrame* frameBufferAtIndex(size_t) OVERRIDE;
         virtual bool frameIsCompleteAtIndex(size_t) const OVERRIDE;
         virtual float frameDurationAtIndex(size_t) const OVERRIDE;
+        virtual size_t clearCacheExceptFrame(size_t) OVERRIDE;
         // CAUTION: setFailed() deletes |m_reader|.  Be careful to avoid
         // accessing deleted memory, especially when calling this from inside
         // GIFImageReader!
         virtual bool setFailed() OVERRIDE;
 
         // Callbacks from the GIF reader.
         bool haveDecodedRow(size_t frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels);
         bool frameComplete(size_t frameIndex);
 
         // For testing.
@@ skipping 17 matching lines @@
         bool initFrameBuffer(size_t frameIndex);
 
         bool m_currentBufferSawAlpha;
         mutable int m_repetitionCount;
         OwnPtr<GIFImageReader> m_reader;
     };
 
 } // namespace WebCore
 
 #endif