Add a new API for testing animated images

Source/core/svg/graphics/SVGImage.h

 /*
  * Copyright (C) 2006 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 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
@@ skipping 45 matching lines @@
     bool isSVGImage() const override { return true; }
     IntSize size() const override { return m_intrinsicSize; }
     void setURL(const KURL& url) { m_url = url; }
 
     bool currentFrameHasSingleSecurityOrigin() const override;
 
     void startAnimation(CatchUpAnimation = CatchUp) override;
     void stopAnimation() override;
     void resetAnimation() override;
 
+    // Advances an animated image. This will trigger an animation update for CSS
+    // and advance the SMIL timeline by one frame.
+    void advanceAnimationForTesting() override;
+
     PassRefPtr<SkImage> imageForCurrentFrame() override;
 
     // Returns the SVG image document's frame.
     FrameView* frameView() const;
 
     // Does the SVG image/document contain any animations?
     bool hasAnimations() const;
 
     void updateUseCounters(Document&) const;
 
@@ skipping 53 matching lines @@
         m_image->setImageObserver(m_observer);
     }
 private:
     Image* m_image;
     ImageObserver* m_observer;
 };
 
 }
 
 #endif // SVGImage_h