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

third_party/WebKit/Source/core/html/canvas/CanvasImageSource.h

Index: third_party/WebKit/Source/core/html/canvas/CanvasImageSource.h
diff --git a/third_party/WebKit/Source/core/html/canvas/CanvasImageSource.h b/third_party/WebKit/Source/core/html/canvas/CanvasImageSource.h
index 2c00cb1defd8e613800d59c614b8f6ed97d05165..fa635722d2007c2c9221a57cb12692b5e16b46df 100644
--- a/third_party/WebKit/Source/core/html/canvas/CanvasImageSource.h
+++ b/third_party/WebKit/Source/core/html/canvas/CanvasImageSource.h
@@ -68,6 +68,9 @@ public:
     virtual const KURL& sourceURL() const { return blankURL(); }
     virtual bool isOpaque() const { return false; }
 
+    virtual int sourceWidth() { return 0; }

[Justin Novosad, 2016/06/23 14:48:43]

This should be pure virtual IMHO. The default behavior of returning 0 is not the
correct result for any of the subclasses

+    virtual int sourceHeight() { return 0; }
+
 protected:
     virtual ~CanvasImageSource() { }
 };