Pull up clearCacheExceptFrame to ImageDecoder.

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 211 matching lines @@
            ImageFrame::DisposeOverwriteBgcolor) &&
           !prevBuffer->hasAlpha() &&
           buffer.originalFrameRect().contains(prevBuffer->originalFrameRect()))
         buffer.setHasAlpha(false);
     }
   }
 
   return true;
 }
 
-size_t GIFImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame) {
-  // We expect that after this call, we'll be asked to decode frames after
-  // this one.  So we want to avoid clearing frames such that those requests
-  // would force re-decoding from the beginning of the image.
-  //
-  // When |clearExceptFrame| is e.g. DisposeKeep, simply not clearing that
-  // frame is sufficient, as the next frame will be based on it, and in
-  // general future frames can't be based on anything previous.
-  //
-  // However, if this frame is DisposeOverwritePrevious, then subsequent
-  // frames will depend on this frame's required previous frame.  In this
-  // case, we need to preserve both this frame and that one.
-  size_t clearExceptFrame2 = kNotFound;
-  if (clearExceptFrame < m_frameBufferCache.size()) {
-    const ImageFrame& frame = m_frameBufferCache[clearExceptFrame];
-    if ((frame.getStatus() != ImageFrame::FrameEmpty) &&
-        (frame.getDisposalMethod() == ImageFrame::DisposeOverwritePrevious)) {
-      clearExceptFrame2 = clearExceptFrame;
-      clearExceptFrame = frame.requiredPreviousFrameIndex();
-    }
-  }
-
-  // Now |clearExceptFrame| indicates the frame that future frames will
-  // depend on.  But if decoding is skipping forward past intermediate frames,
-  // this frame may be FrameEmpty.  So we need to keep traversing back through
-  // the required previous frames until we find the nearest non-empty
-  // ancestor.  Preserving that will minimize the amount of future decoding
-  // needed.
-  while ((clearExceptFrame < m_frameBufferCache.size()) &&
-         (m_frameBufferCache[clearExceptFrame].getStatus() ==
-          ImageFrame::FrameEmpty))
-    clearExceptFrame =
-        m_frameBufferCache[clearExceptFrame].requiredPreviousFrameIndex();
-  return clearCacheExceptTwoFrames(clearExceptFrame, clearExceptFrame2);
-}
-
 void GIFImageDecoder::clearFrameBuffer(size_t frameIndex) {
   if (m_reader &&
       m_frameBufferCache[frameIndex].getStatus() == ImageFrame::FramePartial) {
     // Reset the state of the partial frame in the reader so that the frame
     // can be decoded again when requested.
     m_reader->clearDecodeState(frameIndex);
   }
   ImageDecoder::clearFrameBuffer(frameIndex);
 }
 
@@ skipping 61 matching lines @@
   m_currentBufferSawAlpha = false;
 }
 
 bool GIFImageDecoder::canReusePreviousFrameBuffer(size_t frameIndex) const {
   DCHECK(frameIndex < m_frameBufferCache.size());
   return m_frameBufferCache[frameIndex].getDisposalMethod() !=
          ImageFrame::DisposeOverwritePrevious;
 }
 
 }  // namespace blink