Animated WebP: Optimize decoding in case of seeking

Source/core/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 279 matching lines @@
         return;
     }
 
     const size_t oldSize = m_frameBufferCache.size();
     m_frameBufferCache.resize(m_reader->imagesCount());
 
     for (size_t i = oldSize; i < m_reader->imagesCount(); ++i) {
         ImageFrame& buffer = m_frameBufferCache[i];
         const GIFFrameContext* frameContext = m_reader->frameContext(i);
         buffer.setPremultiplyAlpha(m_premultiplyAlpha);
-        buffer.setRequiredPreviousFrameIndex(findRequiredPreviousFrame(i));
+        buffer.setRequiredPreviousFrameIndex(findRequiredPreviousFrame(i, false));
         buffer.setDuration(frameContext->delayTime());
         buffer.setDisposalMethod(frameContext->disposalMethod());
 
         // Initialize the frame rect in our buffer.
         IntRect frameRect = frameContext->frameRect();
 
         // Make sure the frameRect doesn't extend outside the buffer.
         if (frameRect.maxX() > size().width())
             frameRect.setWidth(size().width() - frameRect.x());
         if (frameRect.maxY() > size().height())
@@ skipping 65 matching lines @@
 
     // Update our status to be partially complete.
     buffer->setStatus(ImageFrame::FramePartial);
 
     // Reset the alpha pixel tracker for this frame.
     m_currentBufferSawAlpha = false;
     return true;
 }
 
 } // namespace WebCore