Eliminate copies of encoded image data

third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.h

 /*
  * Copyright (C) 2012 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 13 matching lines @@
  */
 
 #ifndef DeferredImageDecoder_h
 #define DeferredImageDecoder_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/image-decoders/ImageDecoder.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkPixelRef.h"
+#include "third_party/skia/src/core/SkRWBuffer.h"
 #include "wtf/Allocator.h"
 #include "wtf/Forward.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/Vector.h"
 
 class SkImage;
 
 namespace blink {
 
 class ImageFrameGenerator;
@@ skipping 37 matching lines @@
     explicit DeferredImageDecoder(PassOwnPtr<ImageDecoder> actualDecoder);
 
     friend class DeferredImageDecoderTest;
     ImageFrameGenerator* frameGenerator() { return m_frameGenerator.get(); }
 
     void activateLazyDecoding();
     void prepareLazyDecodedFrames();
 
     PassRefPtr<SkImage> createFrameImageAtIndex(size_t index, bool knownToBeOpaque) const;
 
-    RefPtr<SharedBuffer> m_data;
+    // Copy of the data that is passed in, used by deferred decoding.
+    // Allows snapping readonly readers off to use in another thread.

[Peter Kasting, 2016/03/23 02:42:58]

"snapping"?

[scroggo_chromium, 2016/03/24 13:59:45]

I'll update the comment. FWIW, I meant "snapping" as in "snapshot" - the reader
can only read up to the data that had been received when it was created.

+    OwnPtr<SkRWBuffer> m_rwBuffer;
     bool m_allDataReceived;
-    unsigned m_lastDataSize;
     OwnPtr<ImageDecoder> m_actualDecoder;
 
     String m_filenameExtension;
     IntSize m_size;
     int m_repetitionCount;
     bool m_hasColorProfile;
     bool m_canYUVDecode;
 
     // Carries only frame state and other information. Does not carry bitmap.
     Vector<FrameData> m_frameData;
     RefPtr<ImageFrameGenerator> m_frameGenerator;
 
     static bool s_enabled;
 };
 
 } // namespace blink
 
 #endif