Make 2D canvas smarter about chosing whether or not to use GPU acceleration

Source/platform/graphics/GraphicsTypes.h

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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 57 matching lines @@
     CompositeDestinationAtop,
     CompositeXOR,
     CompositePlusLighter
 };
 
 enum OpacityMode {
     NonOpaque,
     Opaque,
 };
 
+enum AccelerationHint {
+    PreferAcceleration,
+    PreferNoAcceleration,
+};
+
 // TODO(junov): crbug.com/453113 relocate ShadowMode to CanvasRenderingContext2DState.h once
 // GraphicsContext no longer uses it.
 enum ShadowMode {
     DrawShadowAndForeground,
     DrawShadowOnly,
     DrawForegroundOnly
 };
 
 enum AntiAliasingMode {
     NotAntiAliased,
@@ skipping 53 matching lines @@
 
 PLATFORM_EXPORT String textAlignName(TextAlign);
 PLATFORM_EXPORT bool parseTextAlign(const String&, TextAlign&);
 
 PLATFORM_EXPORT String textBaselineName(TextBaseline);
 PLATFORM_EXPORT bool parseTextBaseline(const String&, TextBaseline&);
 
 } // namespace blink
 
 #endif