Web Animations CSS: Implement CSS Transitions backed on Web Animations model

Source/core/animation/Player.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 38 matching lines @@
     void cancel();
     double currentTime() const;
     void setCurrentTime(double);
     bool paused() const { return !isNull(m_pauseStartTime); }
     void setPaused(bool);
     double playbackRate() const { return m_playbackRate; }
     void setPlaybackRate(double);
     double startTime() const { return m_startTime; }
     double timeDrift() const;
     DocumentTimeline* timeline() { return m_timeline; }
+    TimedItem* source() { return m_content.get(); }
 
 private:
     Player(DocumentTimeline*, TimedItem*);
     static double effectiveTime(double time) { return isNull(time) ? 0 : time; }
     inline double pausedTimeDrift() const;
     inline double currentTimeBeforeDrift() const;
 
     double m_pauseStartTime;
     double m_playbackRate;
     double m_timeDrift;
     const double m_startTime;
 
     RefPtr<TimedItem> m_content;
     DocumentTimeline* const m_timeline;
 };
 
 } // namespace
 
 #endif