Plumb timeToNextEffect through players and animation

Source/core/animation/Player.h

Index: Source/core/animation/Player.h
diff --git a/Source/core/animation/Player.h b/Source/core/animation/Player.h
index 84ea0e49967476deeb1fd416a8c4d884f773db6b..5f975b48d58e356600e2e87aa26b3d7d448646b8 100644
--- a/Source/core/animation/Player.h
+++ b/Source/core/animation/Player.h
@@ -45,7 +45,12 @@ public:
     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+    //  infinity  - if this player is no longer in effect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);