Implement will-change-based GPU rasterization hint

public/platform/WebContentLayer.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 35 matching lines @@
     // Allow the compositor to determine the scale at which the layer should
     // be rasterized based on the layer's hierarchy and transform. This defaults
     // to false.
     virtual void setAutomaticallyComputeRasterScale(bool) { }
 
     // Set to draw a system-defined checkerboard if the compositor would otherwise draw a tile in this layer
     // and the actual contents are unavailable. If false, the compositor will draw the layer's background color
     // for these tiles.
     // Defaults to false.
     virtual void setDrawCheckerboardForMissingTiles(bool) = 0;
+
+    virtual void setHasGpuRasterizationHint(bool) = 0;
 };
 
 } // namespace blink
 
 #endif // WebContentLayer_h