Move GIF decoder's aggressive purge into ImageDecoder

third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp

 /*
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 216 matching lines @@
       clearFrameBuffer(i);
     }
   }
   return frameBytesCleared;
 }
 
 void ImageDecoder::clearFrameBuffer(size_t frameIndex) {
   m_frameBufferCache[frameIndex].clearPixelData();
 }
 
+void ImageDecoder::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();
+  const uint64_t frameMemoryUsage = frameArea * 4;  // 4 bytes per pixel
+  if (frameMemoryUsage / 4 != frameArea) {          // overflow occurred
+    m_purgeAggressively = true;
+    return;
+  }
+
+  const uint64_t totalMemoryUsage = frameMemoryUsage * index;
+  if (totalMemoryUsage / frameMemoryUsage != index) {  // overflow occurred
+    m_purgeAggressively = true;
+    return;
+  }
+
+  if (totalMemoryUsage > m_maxDecodedBytes) {
+    m_purgeAggressively = true;
+  }
+}
+
 size_t ImageDecoder::findRequiredPreviousFrame(size_t frameIndex,
                                                bool frameRectIsOpaque) {
   ASSERT(frameIndex <= m_frameBufferCache.size());
   if (!frameIndex) {
     // The first frame doesn't rely on any previous data.
     return kNotFound;
   }
 
   const ImageFrame* currBuffer = &m_frameBufferCache[frameIndex];
   if ((frameRectIsOpaque ||
@@ skipping 180 matching lines @@
 
   // FIXME: Don't force perceptual intent if the image profile contains an
   // intent.
   m_sourceToOutputDeviceColorTransform.reset(
       qcms_transform_create(inputProfile.get(), dataFormat, gTargetColorProfile,
                             QCMS_DATA_RGBA_8, QCMS_INTENT_PERCEPTUAL));
 #endif  // USE(QCMSLIB)
 }
 
 }  // namespace blink