Revert of Web Animations: Remove AnimationPlayer discarding logic

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 193 matching lines @@
         // that will be, however, so the parent will need to supply it.
         return forwards
             ? std::numeric_limits<double>::infinity()
             : localTime - end;
     default:
         ASSERT_NOT_REACHED();
         return std::numeric_limits<double>::infinity();
     }
 }
 
+void Animation::notifySampledEffectRemovedFromAnimationStack()
+{
+    ASSERT(m_sampledEffect);
+    m_sampledEffect = nullptr;
+}
+
 #if !ENABLE(OILPAN)
 void Animation::notifyElementDestroyed()
 {
     // If our player is kept alive just by the sampledEffect, we might get our
     // destructor called when we call SampledEffect::clear(), so we need to
     // clear m_sampledEffect first.
     m_target = nullptr;
     clearEventDelegate();
     SampledEffect* sampledEffect = m_sampledEffect;
     m_sampledEffect = nullptr;
@@ skipping 79 matching lines @@
 
 DEFINE_TRACE(Animation)
 {
     visitor->trace(m_target);
     visitor->trace(m_effect);
     visitor->trace(m_sampledEffect);
     AnimationNode::trace(visitor);
 }
 
 } // namespace blink