Enable video painting on Canvas for Chrome on Android.

Source/WebCore/platform/graphics/MediaPlayer.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 316 matching lines @@
 
     bool hasClosedCaptions() const;
     void setClosedCaptionsVisible(bool closedCaptionsVisible);
 
     bool autoplay() const;    
     void setAutoplay(bool);
 
     void paint(GraphicsContext*, const IntRect&);
     void paintCurrentFrameInContext(GraphicsContext*, const IntRect&);
 
+    // copyVideoTextureToCanvas() is a hardware accelerated version of paintCurrentFrameInContext when video is hardware decoded.
+    // It is used to do a GPU-GPU textures copy without readback to system memory if possible. When the Canvas is hardware accelerated, it
+    // will copy the video texture to the canvas texture. But when the Canvas is software based, it will still readback the video
+    // texture to system memory, then draw it onto the Canvas.
+
+    // Each platform port can have its own implementation on this function. The default implementation for it is a single "return false" in MediaPlayerPrivate.h.
+    // In chromium, the implementation is based on GL_CHROMIUM_copy_texture extension which is documented at
+    // http://src.chromium.org/viewvc/chrome/trunk/src/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_copy_texture.txt and implemented at
+    // http://src.chromium.org/viewvc/chrome/trunk/src/gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.cc via shaders.
+    bool copyVideoTextureToCanvas(GraphicsContext*, GraphicsContext3D*);
+
     // copyVideoTextureToPlatformTexture() is used to do the GPU-GPU textures copy without a readback to system memory.
     // The first five parameters denote the corresponding GraphicsContext, destination texture, requested level, requested type and the required internalFormat for destination texture.
     // The last two parameters premultiplyAlpha and flipY denote whether addtional premultiplyAlpha and flip operation are required during the copy.
     // It returns true on success and false on failure.
 
     // In the GPU-GPU textures copy, the source texture(Video texture) should have valid target, internalFormat and size, etc.
     // The destination texture may need to be resized to to the dimensions of the source texture or re-defined to the required internalFormat.
     // The current restrictions require that format shoud be RGB or RGBA, type should be UNSIGNED_BYTE and level should be 0. It may be lifted in the future.
 
     // Each platform port can have its own implementation on this function. The default implementation for it is a single "return false" in MediaPlayerPrivate.h.
@@ skipping 166 matching lines @@
 typedef void (*MediaEngineClearMediaCacheForSite)(const String&);
 
 typedef void (*MediaEngineRegistrar)(CreateMediaEnginePlayer, MediaEngineSupportedTypes, MediaEngineSupportsType,
     MediaEngineGetSitesInMediaCache, MediaEngineClearMediaCache, MediaEngineClearMediaCacheForSite);
 
 }
 
 #endif // ENABLE(VIDEO)
 
 #endif