Move GIF decoder's aggressive purge into 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 18 matching lines @@
 #include "wtf/NotFound.h"
 #include "wtf/PtrUtil.h"
 #include <limits>
 
 namespace blink {
 
 GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption,
                                  GammaAndColorProfileOption colorOptions,
                                  size_t maxDecodedBytes)
     : ImageDecoder(alphaOption, colorOptions, maxDecodedBytes),
-      m_purgeAggressively(false),
       m_repetitionCount(cAnimationLoopOnce) {}
 
 GIFImageDecoder::~GIFImageDecoder() {}
 
 void GIFImageDecoder::onSetData(SegmentReader* data) {
   if (m_reader)
     m_reader->setData(data);
 }
 
 int GIFImageDecoder::repetitionCount() const {
@@ skipping 346 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;
 }
-
-void GIFImageDecoder::updateAggressivePurging(size_t index) {
-  if (m_purgeAggressively)
-    return;
-
-  // We don't want to cache so much that we cause a memory issue.
-  //
-  // If we used a LRU cache we would fill it and then on next animation loop
-  // we would need to decode all the frames again -- the LRU would give no
-  // benefit and would consume more memory.
-  // So instead, simply purge unused frames if caching all of the frames of
-  // the image would use more memory than the image decoder is allowed
-  // (m_maxDecodedBytes) or would overflow 32 bits..
-  //
-  // As we decode we will learn the total number of frames, and thus total
-  // possible image memory used.
-
-  const uint64_t frameArea = decodedSize().area();
-  // We are about to multiply by 4, which may require an extra bit of storage
-  bool wouldOverflow = frameArea > (UINT64_C(1) << 62);
-  if (wouldOverflow) {
-    m_purgeAggressively = true;
-    return;
-  }
-
-  const uint64_t frameMemoryUsage = frameArea * 4;  // 4 bytes per pixel
-  // We are about to multiply by a size_t, which does not have a fixed
-  // size.
-  // To simplify things, let's make sure our per-frame memory usage and
-  // index can be stored in 32 bits and store the multiplicand in a 64-bit
-  // number.
-  wouldOverflow =
-      (frameMemoryUsage > (UINT32_C(1) << 31)) || (index > (UINT32_C(1) << 31));
-  if (wouldOverflow) {
-    m_purgeAggressively = true;
-    return;
-  }
-
-  const uint64_t totalMemoryUsage = frameMemoryUsage * index;
-  if (totalMemoryUsage > m_maxDecodedBytes) {
-    m_purgeAggressively = true;
-  }
-}
 }  // namespace blink