Add a new API for testing animated images

Source/platform/graphics/Image.h

 /*
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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 103 matching lines @@
     virtual void resetAnimation() {}
 
     // True if this image can potentially animate.
     virtual bool maybeAnimated() { return false; }
 
     // Set animationPolicy
     virtual void setAnimationPolicy(ImageAnimationPolicy) { }
     virtual ImageAnimationPolicy animationPolicy() { return ImageAnimationPolicyAllowed; }
     virtual void advanceTime(double deltaTimeInSeconds) { }
 
+    // Advances an animated image. For BitmapImage (e.g., animated gifs) this
+    // will advance to the next frame. For SVGImage, this will trigger an
+    // animation update for CSS and advance the SMIL timeline by one frame.
+    virtual void advanceAnimationForTesting() { }
+
     // Typically the ImageResource that owns us.
     ImageObserver* imageObserver() const { return m_imageObserver; }
     void setImageObserver(ImageObserver* observer) { m_imageObserver = observer; }
 
     enum TileRule { StretchTile, RoundTile, SpaceTile, RepeatTile };
 
     bool deprecatedBitmapForCurrentFrame(SkBitmap*) WARN_UNUSED_RETURN;
 
     virtual PassRefPtr<SkImage> imageForCurrentFrame() = 0;
     virtual PassRefPtr<Image> imageForDefaultFrame();
@@ skipping 20 matching lines @@
     RefPtr<SharedBuffer> m_encodedImageData;
     ImageObserver* m_imageObserver;
 };
 
 #define DEFINE_IMAGE_TYPE_CASTS(typeName) \
     DEFINE_TYPE_CASTS(typeName, Image, image, image->is##typeName(), image.is##typeName())
 
 } // namespace blink
 
 #endif