Add support for Animated PNG

third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp

 /*
  * 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 250 matching lines @@
 
   if (!m_reader) {
     m_reader = WTF::makeUnique<GIFImageReader>(this);
     m_reader->setData(m_data);
   }
 
   if (!m_reader->parse(query))
     setFailed();
 }
 
-void GIFImageDecoder::onInitFrameBuffer(size_t frameIndex) {
+bool GIFImageDecoder::onInitFrameBuffer(size_t frameIndex) {
   m_currentBufferSawAlpha = false;
+  return true;
 }
 
 bool GIFImageDecoder::canReusePreviousFrameBuffer(size_t frameIndex) const {
   DCHECK(frameIndex < m_frameBufferCache.size());
   return m_frameBufferCache[frameIndex].getDisposalMethod() !=
          ImageFrame::DisposeOverwritePrevious;
 }
 
 }  // namespace blink