Reland change to enable deferred image decoding for animated GIFs

Source/core/platform/graphics/chromium/LazyDecodingPixelRef.h

Index: Source/core/platform/graphics/chromium/LazyDecodingPixelRef.h
diff --git a/Source/core/platform/graphics/chromium/LazyDecodingPixelRef.h b/Source/core/platform/graphics/chromium/LazyDecodingPixelRef.h
index 3cb325a1610b87f13a3d662f1664f02aa9fe1329..bb288eb4fad796f7f79bf4221fcc3645b7ab5b07 100644
--- a/Source/core/platform/graphics/chromium/LazyDecodingPixelRef.h
+++ b/Source/core/platform/graphics/chromium/LazyDecodingPixelRef.h
@@ -32,8 +32,8 @@
 #include "SkSize.h"
 #include "SkTypes.h"
 #include "skia/ext/lazy_pixel_ref.h"
+
 #include "wtf/RefPtr.h"
-#include "wtf/ThreadingPrimitives.h"
 
 using skia::LazyPixelRef;
 
@@ -46,12 +46,13 @@ class ScaledImageFragment;
 
 class LazyDecodingPixelRef : public LazyPixelRef {
 public:
-    LazyDecodingPixelRef(PassRefPtr<ImageFrameGenerator>, const SkISize& scaledSize, const SkIRect& scaledSubset);
+    LazyDecodingPixelRef(PassRefPtr<ImageFrameGenerator>, const SkISize& scaledSize, size_t index, const SkIRect& scaledSubset);
     virtual ~LazyDecodingPixelRef();
 
     SK_DECLARE_UNFLATTENABLE_OBJECT()
 
     PassRefPtr<ImageFrameGenerator> frameGenerator() const { return m_frameGenerator; }
+    size_t frameIndex() const { return m_frameIndex; }
     bool isScaled(const SkISize& fullSize) const;
     bool isClipped() const;
 
@@ -71,11 +72,11 @@ protected:
 
 private:
     RefPtr<ImageFrameGenerator> m_frameGenerator;
+    size_t m_frameIndex;
     SkISize m_scaledSize;
     SkIRect m_scaledSubset;
 
     const ScaledImageFragment* m_lockedCachedImage;
-    Mutex m_mutex;
 };
 
 } // namespace WebCore