2D Canvas doesn't blend video with the destination buffer.

content/renderer/media/webmediaplayer_ms.h

Index: content/renderer/media/webmediaplayer_ms.h
diff --git a/content/renderer/media/webmediaplayer_ms.h b/content/renderer/media/webmediaplayer_ms.h
index 7e8944ad92026ca5ada8e8975f96f7d0cbc4f21c..075aeff0dec2bb0c981549505b24a74aa6a2b9fa 100644
--- a/content/renderer/media/webmediaplayer_ms.h
+++ b/content/renderer/media/webmediaplayer_ms.h
@@ -79,6 +79,11 @@ class WebMediaPlayerMS
   // Methods for painting.
   virtual void paint(blink::WebCanvas* canvas,
                      const blink::WebRect& rect,
+                     unsigned char alpha,
+                     SkXfermode::Mode mode);
+  // TODO(dshwang): remove it.
+  virtual void paint(blink::WebCanvas* canvas,
+                     const blink::WebRect& rect,
                      unsigned char alpha);
 
   // True if the loaded media has a playable video/audio track.