Reland again "Decode GIF image frames on demand".

Source/core/platform/graphics/BitmapImage.h

 /*
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2008-2009 Torch Mobile, Inc.
  *
  * 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 88 matching lines @@
     static PassRefPtr<BitmapImage> create(PassNativeImagePtr nativeImage, ImageObserver* observer = 0)
     {
         return adoptRef(new BitmapImage(nativeImage, observer));
     }
     static PassRefPtr<BitmapImage> create(ImageObserver* observer = 0)
     {
         return adoptRef(new BitmapImage(observer));
     }
     virtual ~BitmapImage();
     
-    virtual bool isBitmapImage() const;
+    virtual bool isBitmapImage() const OVERRIDE;
 
-    virtual bool hasSingleSecurityOrigin() const;
+    virtual bool hasSingleSecurityOrigin() const OVERRIDE;
 
-    virtual IntSize size() const;
+    virtual IntSize size() const OVERRIDE;
     IntSize sizeRespectingOrientation() const;
     IntSize currentFrameSize() const;
-    virtual bool getHotSpot(IntPoint&) const;
+    virtual bool getHotSpot(IntPoint&) const OVERRIDE;
 
-    virtual bool dataChanged(bool allDataReceived);
-    virtual String filenameExtension() const;
+    virtual bool dataChanged(bool allDataReceived) OVERRIDE;
+    virtual String filenameExtension() const OVERRIDE;
 
     // It may look unusual that there is no start animation call as public API.  This is because
     // we start and stop animating lazily.  Animation begins whenever someone draws the image.  It will
     // automatically pause once all observers no longer want to render the image anywhere.
-    virtual void stopAnimation();
-    virtual void resetAnimation();
+    virtual void stopAnimation() OVERRIDE;
+    virtual void resetAnimation() OVERRIDE;
 
-    virtual unsigned decodedSize() const;
+    virtual unsigned decodedSize() const OVERRIDE;
 
     virtual PassNativeImagePtr nativeImageForCurrentFrame() OVERRIDE;
     virtual bool currentFrameKnownToBeOpaque() OVERRIDE;
 
     ImageOrientation currentFrameOrientation();
 
 #if !ASSERT_DISABLED
-    virtual bool notSolidColor();
+    virtual bool notSolidColor() OVERRIDE;
 #endif
 
     void reportMemoryUsage(MemoryObjectInfo*) const OVERRIDE;
 
 private:
     void updateSize() const;
 
 protected:
     enum RepetitionCountStatus {
       Unknown,    // We haven't checked the source's repetition count.
       Uncertain,  // We have a repetition count, but it might be wrong (some GIFs have a count after the image data, and will report "loop once" until all data has been decoded).
       Certain     // The repetition count is known to be correct.
     };
 
     BitmapImage(PassNativeImagePtr, ImageObserver* = 0);
     BitmapImage(ImageObserver* = 0);
 
-    virtual void draw(GraphicsContext*, const FloatRect& dstRect, const FloatRect& srcRect, ColorSpace styleColorSpace, CompositeOperator, BlendMode);
+    virtual void draw(GraphicsContext*, const FloatRect& dstRect, const FloatRect& srcRect, ColorSpace styleColorSpace, CompositeOperator, BlendMode) OVERRIDE;
     virtual void draw(GraphicsContext*, const FloatRect& dstRect, const FloatRect& srcRect, ColorSpace styleColorSpace, CompositeOperator, BlendMode, RespectImageOrientationEnum) OVERRIDE;
 
     size_t currentFrame() const { return m_currentFrame; }
-    virtual size_t frameCount();
+    size_t frameCount();
     PassNativeImagePtr frameAtIndex(size_t);
     bool frameIsCompleteAtIndex(size_t);
     float frameDurationAtIndex(size_t);
     bool frameHasAlphaAtIndex(size_t);
     ImageOrientation frameOrientationAtIndex(size_t);
 
     // Decodes and caches a frame. Never accessed except internally.
     void cacheFrame(size_t index);
     // Called before accessing m_frames[index]. Returns false on index out of bounds.
     bool ensureFrameIsCached(size_t index);
 
-    // Called to invalidate cached data. When |destroyAll| is true, we wipe out
-    // the entire frame buffer cache and tell the image source to destroy
-    // everything; this is used when e.g. we want to free some room in the image
-    // cache. If |destroyAll| is false, we only delete frames up to the current
-    // one; this is used while animating large images to keep memory footprint
-    // low without redecoding the whole image on every frame.
-    virtual void destroyDecodedData(bool destroyAll = true);
+    // Called to invalidate cached data. This is used while animating large
+    // images to keep memory footprint low. The decoder may preserve some frames
+    // to avoid redecoding the whole image on every frame.
+    virtual void destroyDecodedData() OVERRIDE;
 
-    // If the image is large enough, calls destroyDecodedData() and passes
-    // |destroyAll| along.
-    void destroyDecodedDataIfNecessary(bool destroyAll);
+    // If the image is large enough, calls destroyDecodedData().
+    void destroyDecodedDataIfNecessary();
 
     // Generally called by destroyDecodedData(), destroys whole-image metadata
     // and notifies observers that the memory footprint has (hopefully)
     // decreased by |frameBytesCleared|.
-    void destroyMetadataAndNotify(unsigned frameBytesCleared);
+    void destroyMetadataAndNotify(size_t frameBytesCleared);
 
     // Whether or not size is available yet.    
     bool isSizeAvailable();
 
     // Called after asking the source for any information that may require
     // decoding part of the image (e.g., the image size).  We need to report
     // the partially decoded data to our observer so it has an accurate
     // account of the BitmapImage's memory usage.
     void didDecodeProperties() const;
 
     // Animation.
     int repetitionCount(bool imageKnownToBeComplete);  // |imageKnownToBeComplete| should be set if the caller knows the entire image has been decoded.
     bool shouldAnimate();
-    virtual void startAnimation(bool catchUpIfNecessary = true);
+    virtual void startAnimation(bool catchUpIfNecessary = true) OVERRIDE;
     void advanceAnimation(Timer<BitmapImage>*);
 
     // Function that does the real work of advancing the animation.  When
     // skippingFrames is true, we're in the middle of a loop trying to skip over
     // a bunch of animation frames, so we should not do things like decode each
     // one or notify our observers.
     // Returns whether the animation was advanced.
     bool internalAdvanceAnimation(bool skippingFrames);
 
     // Checks to see if the image is a 1x1 solid color.  We optimize these images and just do a fill rect instead.
@@ skipping 31 matching lines @@
     bool m_allDataReceived : 1; // Whether or not we've received all our data.
     mutable bool m_haveSize : 1; // Whether or not our |m_size| member variable has the final overall image size yet.
     bool m_sizeAvailable : 1; // Whether or not we can obtain the size of the first image frame yet from ImageIO.
     mutable bool m_hasUniformFrameSize : 1;
     mutable bool m_haveFrameCount : 1;
 };
 
 }
 
 #endif