Add a new API for testing animated images

Source/core/testing/Internals.idl

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 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.
@@ skipping 60 matching lines @@
 
     // Animation testing.
     [RaisesException] void pauseAnimations(double pauseTime);
     bool isCompositedAnimation(Animation animation);
     void disableCompositedAnimation(Animation animation);
 
     // Modifies m_desiredFrameStartTime in BitmapImage to advance the next frame time
     // for testing whether animated images work properly.
     [RaisesException] void advanceTimeForImage(Element image, 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.
+    [RaisesException, TypeChecking=Interface] void advanceImageAnimation(Element image);
+
     [RaisesException, TypeChecking=Interface] Node nextSiblingInComposedTree(Node node);
     [RaisesException, TypeChecking=Interface] Node firstChildInComposedTree(Node node);
     [RaisesException, TypeChecking=Interface] Node lastChildInComposedTree(Node node);
     [RaisesException, TypeChecking=Interface] Node nextInComposedTree(Node node);
     [RaisesException, TypeChecking=Interface] Node previousInComposedTree(Node node);
 
     DOMString visiblePlaceholder(Element element);
 
     [TypeChecking=Interface] void selectColorInColorChooser(Element element, DOMString colorValue);
     [TypeChecking=Interface] void endColorChooser(Element element);
@@ skipping 247 matching lines @@
 
     ClientRectList outlineRects(Element element);
     void setCapsLockState(boolean enabled);
 
     // Returns whether the scrollbar was able to be shown or hidden; not all platforms
     // support overlay scrollbars.
     bool setScrollbarVisibilityInScrollableArea(Node node, boolean visible);
 
     void forceRestrictIFramePermissions();
 };