Free temporary GPU and memory resources held by inactive or hidden 2D canvases

Source/platform/graphics/ImageBuffer.h

 /*
  * Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2007, 2008, 2009 Apple Inc. All rights reserved.
  * 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 63 matching lines @@
     WTF_MAKE_NONCOPYABLE(ImageBuffer); WTF_MAKE_FAST_ALLOCATED;
 public:
     static PassOwnPtr<ImageBuffer> create(const IntSize&, OpacityMode = NonOpaque);
     static PassOwnPtr<ImageBuffer> create(PassOwnPtr<ImageBufferSurface>);
 
     ~ImageBuffer();
 
     const IntSize& size() const { return m_surface->size(); }
     bool isAccelerated() const { return m_surface->isAccelerated(); }
 
+    void setIsHidden(bool hidden) { m_surface->setIsHidden(hidden); }
+
     GraphicsContext* context() const;
 
     const SkBitmap& bitmap() const;
 
     PassRefPtr<Image> copyImage(BackingStoreCopy = CopyBackingStore, ScaleBehavior = Scaled) const;
     // Give hints on the faster copyImage Mode, return DontCopyBackingStore if it supports the DontCopyBackingStore behavior
     // or return CopyBackingStore if it doesn't.
     static BackingStoreCopy fastCopyImageMode();
 
     PassRefPtr<Uint8ClampedArray> getUnmultipliedImageData(const IntRect&) const;
@@ skipping 41 matching lines @@
 
     IntSize m_size;
     RefPtr<Uint8ClampedArray> m_data;
 };
 
 String PLATFORM_EXPORT ImageDataToDataURL(const ImageDataBuffer&, const String& mimeType, const double* quality);
 
 } // namespace WebCore
 
 #endif // ImageBuffer_h