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

Source/core/animation/AnimationPlayer.cpp

 /*
  * 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 129 matching lines @@
     if (m_held) {
         setCurrentTimeInternal(m_holdTime, reason);
         return;
     }
     if (!limited(calculateCurrentTime()))
         return;
     m_held = true;
     m_holdTime = m_playbackRate < 0 ? 0 : sourceEnd();
 }
 
+double AnimationPlayer::startTime(bool& isNull) const
+{
+    double result = startTime();
+    isNull = std::isnan(result);
+    return result;
+}
+
 double AnimationPlayer::startTime() const
 {
     return m_startTime * 1000;
 }
 
+double AnimationPlayer::currentTime(bool& isNull)
+{
+    double result = currentTime();
+    isNull = std::isnan(result);
+    return result;
+}
+
 double AnimationPlayer::currentTime()
 {
     if (m_currentTimePending || m_idle)
         return std::numeric_limits<double>::quiet_NaN();
     return currentTimeInternal() * 1000;
 }
 
 double AnimationPlayer::currentTimeInternal()
 {
     updateCurrentTimingState(TimingUpdateOnDemand);
@@ skipping 514 matching lines @@
 
 void AnimationPlayer::trace(Visitor* visitor)
 {
     visitor->trace(m_content);
     visitor->trace(m_timeline);
     visitor->trace(m_pendingFinishedEvent);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace