Remove unused entry point rateLimitOffscreenContextCHROMIUM from WebGraphicsContext3D

public/platform/WebExternalTextureLayer.h

 /*
  * Copyright (C) 2011 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 39 matching lines @@
     // Sets whether every pixel in this layer is opaque. Defaults to false.
     virtual void setOpaque(bool) = 0;
 
     // Sets whether this layer's texture has premultiplied alpha or not. Defaults to true.
     virtual void setPremultipliedAlpha(bool) = 0;
 
     // Sets whether the texture should be blended with the background color
     // at draw time. Defaults to false.
     virtual void setBlendBackgroundColor(bool) = 0;
 
-    // Sets whether this context should be rate limited by the compositor. Rate limiting works by blocking
-    // invalidate() and invalidateRect() calls if the compositor is too many frames behind.
-    virtual void setRateLimitContext(bool) = 0;
-
     // Sets whether this texture should use nearest neighbor interpolation as
     // opposed to bilinear. Defaults to false.
     virtual void setNearestNeighbor(bool) = 0;
 };
 
 } // namespace blink
 
 #endif // WebExternalTextureLayer_h