Disable 2D canvas switch to CPU rendering while backgrounded

third_party/WebKit/Source/platform/graphics/Canvas2DLayerBridge.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 43 matching lines @@
 class SharedContextRateLimiter;
 
 #if OS(MACOSX)
 // Canvas hibernation is currently disabled on MacOS X due to a bug that causes content loss
 // TODO: Find a better fix for crbug.com/588434
 #define CANVAS2D_HIBERNATION_ENABLED 0
 #else
 #define CANVAS2D_HIBERNATION_ENABLED 1
 #endif
 
+// TODO: Fix background rendering and remove this workaround. crbug.com/600386
+#define CANVAS2D_BACKGROUND_RENDER_SWITCH_TO_CPU 0
+
 class PLATFORM_EXPORT Canvas2DLayerBridge : public WebExternalTextureLayerClient, public WebThread::TaskObserver, public RefCounted<Canvas2DLayerBridge> {
     WTF_MAKE_NONCOPYABLE(Canvas2DLayerBridge);
 public:
     enum AccelerationMode {
         DisableAcceleration,
         EnableAcceleration,
         ForceAccelerationForTesting,
     };
 
     static PassRefPtr<Canvas2DLayerBridge> create(const IntSize&, int msaaSampleCount, OpacityMode, AccelerationMode);
@@ skipping 122 matching lines @@
     GLenum m_lastFilter;
     AccelerationMode m_accelerationMode;
     OpacityMode m_opacityMode;
     IntSize m_size;
     int m_recordingPixelCount;
 };
 
 } // namespace blink
 
 #endif