Web-Animations: Implement idle state for AnimationPlayers.

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 67 matching lines @@
     void setCurrentTimeInternal(double newCurrentTime, TimingUpdateReason = TimingUpdateOnDemand);
 
     bool paused() const { return m_paused && !m_isPausedForTesting; }
     String playState();
     AnimationPlayState playStateInternal();
 
     void pause();
     void play();
     void reverse();
     void finish(ExceptionState&);
-    bool finished() { return limited(currentTimeInternal()); }
-    bool playing() { return !(finished() || m_paused || m_isPausedForTesting); }
+    bool finished() { return !m_idle && limited(currentTimeInternal()); }
+    bool playing() { return !(finished() || m_paused || m_isPausedForTesting || m_idle); }
     // FIXME: Resolve whether finished() should just return the flag, and
     // remove this method.
     bool finishedInternal() const { return m_finished; }
 
     DEFINE_ATTRIBUTE_EVENT_LISTENER(finish);
 
     virtual const AtomicString& interfaceName() const OVERRIDE;
     virtual ExecutionContext* executionContext() const OVERRIDE;
     virtual bool hasPendingActivity() const OVERRIDE;
     virtual void stop() OVERRIDE;
@@ skipping 103 matching lines @@
             , sourceChanged(false)
             , pendingAction(Start)
         { }
         double startTime;
         double holdTime;
         double playbackRate;
         bool sourceChanged;
         CompositorAction pendingAction;
     };
 
+    void uncancel()
+    {
+        if (m_idle) {
+            m_idle = false;
+            m_finished = false;
+            m_held = true;
+            m_holdTime = 0;
+        }
+    }
+
     // This mirrors the known compositor state. It is created when a compositor
     // animation is started. Updated once the start time is known and each time
     // modifications are pushed to the compositor.
     OwnPtr<CompositorState> m_compositorState;
     bool m_compositorPending;
     bool m_currentTimePending;
+    bool m_idle;
 };
 
 } // namespace blink
 
 #endif