Add a new API for testing animated images

Source/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 66 matching lines @@
     // the image is rendered, and automatically pauses once all observers no
     // longer want to render the image.
     void stopAnimation() override;
     void resetAnimation() override;
     bool maybeAnimated() override;
 
     void setAnimationPolicy(ImageAnimationPolicy policy) override { m_animationPolicy = policy; }
     ImageAnimationPolicy animationPolicy() override { return m_animationPolicy; }
     void advanceTime(double deltaTimeInSeconds) override;
 
+    // Advance the image animation by one frame.
+    void advanceAnimationForTesting() override { internalAdvanceAnimation(false); }
+
     PassRefPtr<SkImage> imageForCurrentFrame() override;
     PassRefPtr<Image> imageForDefaultFrame() override;
     bool currentFrameKnownToBeOpaque() override;
     bool currentFrameIsComplete() override;
     bool currentFrameIsLazyDecoded() override;
 
     ImageOrientation currentFrameOrientation();
 
 private:
     friend class BitmapImageTest;
@@ skipping 91 matching lines @@
     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;
 };
 
 DEFINE_IMAGE_TYPE_CASTS(BitmapImage);
 
 } // namespace blink
 
 #endif