Oilpan: KeyframeEffect::m_target shouldn't become stale

Source/core/animation/ElementAnimations.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 56 matching lines @@
 
     void restartAnimationOnCompositor();
 
     void updateAnimationFlags(ComputedStyle&);
     void setAnimationStyleChange(bool animationStyleChange) { m_animationStyleChange = animationStyleChange; }
 
     const ComputedStyle* baseComputedStyle() const;
     void updateBaseComputedStyle(const ComputedStyle*);
     void clearBaseComputedStyle();
 
+#if !ENABLE(OILPAN)
+    void addEffect(KeyframeEffect* effect) { m_effects.add(effect); }
+#endif
+
     DECLARE_TRACE();
 
 private:
     bool isAnimationStyleChange() const;
 
     AnimationStack m_defaultStack;
     CSSAnimations m_cssAnimations;
     AnimationCountedSet m_animations;
     bool m_animationStyleChange;
     RefPtr<ComputedStyle> m_baseComputedStyle;
 
+#if !ENABLE(OILPAN)
+    // TODO(oilpan): This is to avoid a reference cycle that keeps Elements
+    // alive and won't be needed once the Node hierarchy becomes traceable.
+    HeapHashSet<WeakMember<KeyframeEffect>> m_effects;
+#endif
+
     // CSSAnimations and DeferredLegacyStyleInterpolation checks if a style change is due to animation.
     friend class CSSAnimations;
     friend class DeferredLegacyStyleInterpolation;
 };
 
 } // namespace blink
 
 #endif // ElementAnimations_h