Blink CompositorAnimations: Do not crash if no compositor animation player.

third_party/WebKit/Source/core/animation/CompositorAnimations.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 365 matching lines @@
     if (!canStartAnimationOnCompositor(element)) {
         // When an element is being detached, we cancel any associated
         // Animations for CSS animations. But by the time we get
         // here the mapping will have been removed.
         // FIXME: Defer remove/pause operations until after the
         // compositing update.
         return;
     }
     if (RuntimeEnabledFeatures::compositorAnimationTimelinesEnabled()) {
         WebCompositorAnimationPlayer* compositorPlayer = animation.compositorPlayer();
-        ASSERT(compositorPlayer);
-        compositorPlayer->removeAnimation(id);
+        if (compositorPlayer)
+            compositorPlayer->removeAnimation(id);
     } else {
         toLayoutBoxModelObject(element.layoutObject())->layer()->compositedLayerMapping()->mainGraphicsLayer()->removeAnimation(id);
     }
 }
 
 void CompositorAnimations::pauseAnimationForTestingOnCompositor(const Element& element, const Animation& animation, int id, double pauseTime)
 {
     // FIXME: canStartAnimationOnCompositor queries compositingState, which is not necessarily up to date.
     // https://code.google.com/p/chromium/issues/detail?id=339847
     DisableCompositingQueryAsserts disabler;
@@ skipping 359 matching lines @@
             break;
         default:
             ASSERT_NOT_REACHED();
         }
         animations.append(animation.release());
     }
     ASSERT(!animations.isEmpty());
 }
 
 } // namespace blink