Improving canvas 2D performance by switching graphics rendering pipeline.

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

 /*
  * Copyright (C) 2004, 2006, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 244 matching lines @@
     // It prevents HTMLCanvasElement::buffer() from continuously re-attempting to allocate an imageBuffer
     // after the first attempt failed.
     mutable bool m_didFailToCreateImageBuffer;
     bool m_imageBufferIsClear;
     std::unique_ptr<ImageBuffer> m_imageBuffer;
 
     mutable RefPtr<Image> m_copiedImage; // FIXME: This is temporary for platforms that have to copy the image buffer to render (and for CSSCanvasValue).
 
     // Used for OffscreenCanvas that controls this HTML canvas element
     std::unique_ptr<CanvasSurfaceLayerBridge> m_surfaceLayerBridge;
+
+    int m_numFramesSinceLastRenderingModeSwitch;
+    bool m_pendingRenderingModeSwitch;
 };
 
 } // namespace blink
 
 #endif // HTMLCanvasElement_h