Rename LifecycleObserver<T>::dispose() as clearContext()

Source/core/animation/Animation.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 102 matching lines @@
     if (m_timeline)
         m_timeline->animationDestroyed(this);
 #endif
 
     destroyCompositorPlayer();
 }
 
 #if !ENABLE(OILPAN)
 void Animation::detachFromTimeline()
 {
-    dispose();
     m_timeline = nullptr;
+    ActiveDOMObject::clearContext();
 }
 #endif
 
 double Animation::sourceEnd() const
 {
     return m_content ? m_content->endTimeInternal() : 0;
 }
 
 bool Animation::limited(double currentTime) const
 {
@@ skipping 889 matching lines @@
     visitor->trace(m_content);
     visitor->trace(m_timeline);
     visitor->trace(m_pendingFinishedEvent);
     visitor->trace(m_finishedPromise);
     visitor->trace(m_readyPromise);
     EventTargetWithInlineData::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace