Web Animations: Don't set compositor pending when document has been detached

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 725 matching lines @@
     if (!hasActiveAnimationsOnCompositor()) {
         destroyCompositorPlayer();
         m_compositorState.release();
     }
     if (effectChanged && m_compositorState) {
         m_compositorState->effectChanged = true;
     }
     if (m_compositorPending || m_isPausedForTesting) {
         return;
     }
+#if !ENABLE(OILPAN)
+    if (!timeline() || !timeline()->document()) {
+        return;
+    }
+#endif
 
     if (!m_compositorState || m_compositorState->effectChanged
         || !playing() || m_compositorState->playbackRate != m_playbackRate
         || m_compositorState->startTime != m_startTime) {
         m_compositorPending = true;
-        ASSERT(timeline());
-        ASSERT(timeline()->document());
         timeline()->document()->compositorPendingAnimations().add(this);
     }
 }
 
 void Animation::cancelAnimationOnCompositor()
 {
     if (hasActiveAnimationsOnCompositor())
         toKeyframeEffect(m_content.get())->cancelAnimationOnCompositor();
 
     destroyCompositorPlayer();
@@ skipping 324 matching lines @@
     visitor->trace(m_content);
     visitor->trace(m_timeline);
     visitor->trace(m_pendingFinishedEvent);
     visitor->trace(m_finishedPromise);
     visitor->trace(m_readyPromise);
     RefCountedGarbageCollectedEventTargetWithInlineData<Animation>::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace