Plumb timeToNextEffect through players and animation

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 27 matching lines @@
 
 class DocumentTimeline;
 
 class Player FINAL : public RefCounted<Player> {
 
 public:
     ~Player();
     static PassRefPtr<Player> create(DocumentTimeline*, TimedItem*);
 
     // Returns whether this player is still current or in effect.
-    bool update();
+    // timeToEffectChange returns:
+    //  infinity  - if this player is no longer in effect
+    //  0         - if this player requires an update on the next frame
+    //  n         - if this player requires an update after 'n' units of time
+    bool update(double* timeToEffectChange = 0);
+
     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; }
@@ skipping 10 matching lines @@
     double m_timeDrift;
     const double m_startTime;
 
     RefPtr<TimedItem> m_content;
     DocumentTimeline* const m_timeline;
 };
 
 } // namespace
 
 #endif