Don't cache any SkBitmaps in DeferredImageDecoder

Source/platform/image-decoders/ImageDecoder.h

Index: Source/platform/image-decoders/ImageDecoder.h
diff --git a/Source/platform/image-decoders/ImageDecoder.h b/Source/platform/image-decoders/ImageDecoder.h
index 178b6f57dc590c456945b12db5bef28459c9c99e..72d3edae2f6c68b6351c2f709c0791670bd8a9e2 100644
--- a/Source/platform/image-decoders/ImageDecoder.h
+++ b/Source/platform/image-decoders/ImageDecoder.h
@@ -47,6 +47,24 @@ typedef Vector<char> ColorProfile;
 
 namespace blink {
 
+// GIF and WebP support animation. The explanation below is in terms of GIF,
+// but the same constants are used for WebP, too.
+// GIFs have an optional 16-bit unsigned loop count that describes how an
+// animated GIF should be cycled.  If the loop count is absent, the animation
+// cycles once; if it is 0, the animation cycles infinitely; otherwise the
+// animation plays n + 1 cycles (where n is the specified loop count).  If the
+// GIF decoder defaults to cAnimationLoopOnce in the absence of any loop count
+// and translates an explicit "0" loop count to cAnimationLoopInfinite, then we
+// get a couple of nice side effects:
+//   * By making cAnimationLoopOnce be 0, we allow the animation cycling code in
+//     BitmapImage.cpp to avoid special-casing it, and simply treat all
+//     non-negative loop counts identically.
+//   * By making the other two constants negative, we avoid conflicts with any
+//     real loop count values.
+const int cAnimationLoopOnce = 0;
+const int cAnimationLoopInfinite = -1;
+const int cAnimationNone = -2;
+
 // ImagePlanes can be used to decode color components into provided buffers instead of using an ImageFrame.
 class PLATFORM_EXPORT ImagePlanes {
 public: