Revert of Web Animations: Remove AnimationPlayer discarding logic

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 144 matching lines @@
     void postCommit(double timelineTime);
 
     unsigned sequenceNumber() const { return m_sequenceNumber; }
     int compositorGroup() const { return m_compositorGroup; }
 
     static bool hasLowerPriority(const AnimationPlayer* player1, const AnimationPlayer* player2)
     {
         return player1->sequenceNumber() < player2->sequenceNumber();
     }
 
+#if !ENABLE(OILPAN)
+    // Checks if the AnimationStack is the last reference holder to the Player.
+    // This won't be needed when AnimationPlayer is moved to Oilpan.
+    bool canFree() const;
+#endif
+
     virtual bool addEventListener(const AtomicString& eventType, PassRefPtr<EventListener>, bool useCapture = false) override;
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     AnimationPlayer(ExecutionContext*, AnimationTimeline&, AnimationNode*);
 
     double sourceEnd() const;
     bool limited(double currentTime) const;
 
@@ skipping 83 matching lines @@
     int m_compositorGroup;
 
     bool m_currentTimePending;
     bool m_stateIsBeingUpdated;
 
 };
 
 } // namespace blink
 
 #endif // AnimationPlayer_h