Declare onFinish event handler for AnimationPlayer

Source/core/animation/DocumentTimeline.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 70 matching lines @@
     bool hasPendingUpdates() const { return !m_playersNeedingUpdate.isEmpty(); }
     double zeroTime() const { return m_zeroTime; }
     double currentTime();
     double effectiveTime();
     void pauseAnimationsForTesting(double);
     size_t numberOfActiveAnimationsForTesting() const;
 
     void setOutdatedAnimationPlayer(AnimationPlayer*);
     bool hasOutdatedAnimationPlayer() const { return m_hasOutdatedAnimationPlayer; }
 
+    Document* document() { return m_document; }
     void detachFromDocument();
 
 protected:
     DocumentTimeline(Document*, PassOwnPtr<PlatformTiming>);
 
 private:
     double m_zeroTime;
     Document* m_document;
     // AnimationPlayers which will be updated on the next frame
     // i.e. current, in effect, or had timing changed
@@ skipping 28 matching lines @@
         Timer<DocumentTimelineTiming> m_timer;
 
     };
 
     friend class AnimationDocumentTimelineTest;
 };
 
 } // namespace
 
 #endif