Blink API to allow mailbox usage with texture layers for WebGL and Canvas2D.

Source/Platform/chromium/public/WebCompositorSupport.h

 /*
  * Copyright (C) 2012 Google 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
@@ skipping 59 matching lines @@
     virtual WebCompositorOutputSurface* createOutputSurfaceForSoftware() { return 0; }
 
     // Layers -------------------------------------------------------
 
     virtual WebLayer* createLayer() { return 0; }
 
     virtual WebContentLayer* createContentLayer(WebContentLayerClient*) { return 0; }
 
     virtual WebExternalTextureLayer* createExternalTextureLayer(WebExternalTextureLayerClient* = 0) { return 0; }
 
+    virtual WebExternalTextureLayer* createExternalTextureLayerForMailbox(WebExternalTextureLayerClient*) { return 0; }

[Ken Russell (switch to Gerrit), 2013/04/05 22:51:02]

It seems weird that there are two entry points (createExternalTextureLayer and
createExternalTextureLayerForMailbox) both taking WebExternalTextureLayerClient.
Maybe WebExternalTextureLayerClient should be subclassed into e.g.
WebExternalTextureMailboxClient and the new entry points added to the subclass.

[alexst (slow to review), 2013/04/06 01:25:38]

Once mailboxes work across the board, the texture ID path should just go away.
My thought was after we flip the switch, we could just delete the old entry
points.

[Ken Russell (switch to Gerrit), 2013/04/08 18:22:56]

OK, that sounds fine.

+
     virtual WebImageLayer* createImageLayer() { return 0; }
 
     virtual WebSolidColorLayer* createSolidColorLayer() { return 0; }
 
     virtual WebScrollbarLayer* createScrollbarLayer(WebScrollbar*, WebScrollbarThemePainter, WebScrollbarThemeGeometry*) { return 0; }
 
 
     // Animation ----------------------------------------------------
 
     virtual WebAnimation* createAnimation(const WebAnimationCurve&, WebAnimation::TargetProperty, int animationId = 0) { return 0; }
 
     virtual WebFloatAnimationCurve* createFloatAnimationCurve() { return 0; }
 
     virtual WebTransformAnimationCurve* createTransformAnimationCurve() { return 0; }
 
     virtual WebTransformOperations* createTransformOperations() { return 0; }
 
 
 protected:
     virtual ~WebCompositorSupport() { }
 };
 
 }
 
 #endif // WebCompositorSupport_h