WebGL: Free temporary GPU resources held by inactive or hidden WebGL.

Source/core/html/canvas/CanvasRenderingContext2D.h

 /*
  * Copyright (C) 2006, 2007, 2009, 2010, 2011, 2012 Apple 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 333 matching lines @@
     void drawFocusRing(const Path&);
 
     void addHitRegionInternal(const HitRegionOptions&, ExceptionState&);
     bool hasClip() { return state().m_hasClip; }
 
     void validateStateStack();
 
     virtual bool is2d() const OVERRIDE { return true; }
     virtual bool isAccelerated() const OVERRIDE;
     virtual bool hasAlpha() const OVERRIDE { return m_hasAlpha; }
+    virtual void setIsHidden(bool) OVERRIDE;
 
     virtual bool isTransformInvertible() const OVERRIDE { return state().m_invertibleCTM; }
 
     virtual blink::WebLayer* platformLayer() const OVERRIDE;
 
     WillBeHeapVector<OwnPtrWillBeMember<State> > m_stateStack;
     OwnPtrWillBeMember<HitRegionManager> m_hitRegionManager;
     bool m_usesCSSCompatibilityParseMode;
     bool m_hasAlpha;
     bool m_isContextLost;
     bool m_contextRestorable;
     Canvas2DContextStorage m_storageMode;
     MutableStylePropertyMap m_fetchedFonts;
     unsigned m_tryRestoreContextAttemptCount;
     Timer<CanvasRenderingContext2D> m_dispatchContextLostEventTimer;
     Timer<CanvasRenderingContext2D> m_dispatchContextRestoredEventTimer;
     Timer<CanvasRenderingContext2D> m_tryRestoreContextEventTimer;
 };
 
 DEFINE_TYPE_CASTS(CanvasRenderingContext2D, CanvasRenderingContext, context, context->is2d(), context.is2d());
 
 } // namespace WebCore
 
 #endif