Web Animations: Use null for unresolved startTime and currentTime in AnimationPlayer

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 52 matching lines @@
     bool update(TimingUpdateReason);
 
     // 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     //  infinity  - if this player is no longer in effect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
     double timeToEffectChange();
 
     void cancel();
 
+    double currentTime(bool& isNull);
     double currentTime();
     void setCurrentTime(double newCurrentTime);
 
     double calculateCurrentTime() const;
     double currentTimeInternal();
     void setCurrentTimeInternal(double newCurrentTime, TimingUpdateReason = TimingUpdateOnDemand);
 
     bool paused() const { return m_paused && !m_isPausedForTesting; }
     String playState();
     AnimationPlayState playStateInternal();
@@ skipping 20 matching lines @@
     void setPlaybackRate(double);
     const AnimationTimeline* timeline() const { return m_timeline; }
     AnimationTimeline* timeline() { return m_timeline; }
 
 #if !ENABLE(OILPAN)
     void timelineDestroyed() { m_timeline = nullptr; }
 #endif
 
     double calculateStartTime(double currentTime) const;
     bool hasStartTime() const { return !isNull(m_startTime); }
+    double startTime(bool& isNull) const;
     double startTime() const;
     double startTimeInternal() const { return m_startTime; }
     void setStartTime(double);
     void setStartTimeInternal(double);
 
     const AnimationNode* source() const { return m_content.get(); }
     AnimationNode* source() { return m_content.get(); }
     void setSource(AnimationNode*);
 
     // Pausing via this method is not reflected in the value returned by
@@ skipping 102 matching lines @@
     // modifications are pushed to the compositor.
     OwnPtr<CompositorState> m_compositorState;
     bool m_compositorPending;
     bool m_currentTimePending;
     bool m_idle;
 };
 
 } // namespace blink
 
 #endif