Add support for Animated PNG

third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp

 /*
  * Copyright (C) 2010 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
@@ skipping 219 matching lines @@
   }
 
   ASSERT(isDecodedSizeAvailable());
 
   size_t frameCount = WebPDemuxGetI(m_demux, WEBP_FF_FRAME_COUNT);
   updateAggressivePurging(frameCount);
 
   return true;
 }
 
-void WEBPImageDecoder::onInitFrameBuffer(size_t frameIndex) {
+bool WEBPImageDecoder::onInitFrameBuffer(size_t frameIndex) {
   // ImageDecoder::initFrameBuffer does a DCHECK if |frameIndex| exists.
   ImageFrame& buffer = m_frameBufferCache[frameIndex];
 
   const size_t requiredPreviousFrameIndex = buffer.requiredPreviousFrameIndex();
   if (requiredPreviousFrameIndex == kNotFound) {
     m_frameBackgroundHasAlpha =
         !buffer.originalFrameRect().contains(IntRect(IntPoint(), size()));
   } else {
     const ImageFrame& prevBuffer =
         m_frameBufferCache[requiredPreviousFrameIndex];
     m_frameBackgroundHasAlpha =
         prevBuffer.hasAlpha() ||
         (prevBuffer.getDisposalMethod() == ImageFrame::DisposeOverwriteBgcolor);
   }
 
   // The buffer is transparent outside the decoded area while the image is
   // loading. The correct alpha value for the frame will be set when it is fully
   // decoded.
   buffer.setHasAlpha(true);
+  return true;
 }
 
 bool WEBPImageDecoder::canReusePreviousFrameBuffer(size_t frameIndex) const {
   DCHECK(frameIndex < m_frameBufferCache.size());
   return m_frameBufferCache[frameIndex].getAlphaBlendSource() !=
          ImageFrame::BlendAtopPreviousFrame;
 }
 
 void WEBPImageDecoder::clearFrameBuffer(size_t frameIndex) {
   if (m_demux && m_demuxState >= WEBP_DEMUX_PARSED_HEADER &&
@@ skipping 239 matching lines @@
         return false;
       }
     // FALLTHROUGH
     default:
       clear();
       return setFailed();
   }
 }
 
 }  // namespace blink