Avoid GPU readback in tex(Sub)Image2D(ImageBitmap)

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

Index: third_party/WebKit/Source/platform/graphics/Image.h
diff --git a/third_party/WebKit/Source/platform/graphics/Image.h b/third_party/WebKit/Source/platform/graphics/Image.h
index 841a2ea4ea92d73524c02e32082db48001097da1..0af64fff5c450ba3bc9beba9b3b00d0e2e082052 100644
--- a/third_party/WebKit/Source/platform/graphics/Image.h
+++ b/third_party/WebKit/Source/platform/graphics/Image.h
@@ -34,6 +34,7 @@
 #include "platform/graphics/ImageAnimationPolicy.h"
 #include "platform/graphics/ImageObserver.h"
 #include "platform/graphics/ImageOrientation.h"
+#include "public/platform/WebGraphicsContext3DProvider.h"
 #include "wtf/Assertions.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/PassRefPtr.h"
@@ -137,7 +138,7 @@ public:
 
     enum TileRule { StretchTile, RoundTile, SpaceTile, RepeatTile };
 
-    virtual PassRefPtr<SkImage> imageForCurrentFrame() = 0;
+    virtual PassRefPtr<SkImage> imageForCurrentFrame(WebGraphicsContext3DProvider* = nullptr) = 0;

[Justin Novosad, 2016/06/09 20:21:29]

The usage of contextProvider argument is non-trivial. You should add comments to
explain it.  Something like: The returned image may or may not be texture
backed, if the caller needs texture backed images to be in a context other that
the shared 3D context (e.g. a WebGL context), the it must specify the desired
context.

[xidachen, 2016/06/10 15:36:08]

Done.

     virtual PassRefPtr<Image> imageForDefaultFrame();
 
     virtual void drawPattern(GraphicsContext&, const FloatRect&,