Web Animations: Allow animations with delay to start on compositor

Source/core/animation/AnimationPlayer.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 59 matching lines @@
     void setPlaybackRate(double);
     const DocumentTimeline* timeline() const { return m_timeline; }
     DocumentTimeline* timeline() { return m_timeline; }
 
     void timelineDestroyed() { m_timeline = 0; }
 
     bool hasStartTime() const { return !isNull(m_startTime); }
     double startTime() const { return m_startTime; }
     void setStartTime(double);
 
+    const TimedItem* source() const { return m_content.get(); }
     TimedItem* source() { return m_content.get(); }
     TimedItem* source(bool& isNull) { isNull = !m_content; return m_content.get(); }
     void setSource(TimedItem*);
 
     double timeLag() { return currentTimeWithoutLag() - currentTime(); }
 
     // Pausing via this method is not reflected in the value returned by
     // paused() and must never overlap with pausing via pause().
     void pauseForTesting(double pauseTime);
     // This should only be used for CSS
@@ skipping 34 matching lines @@
     // This indicates timing information relevant to the player has changed by
     // means other than the ordinary progression of time
     bool m_outdated;
 
     unsigned m_sequenceNumber;
 };
 
 } // namespace
 
 #endif