Oilpan: enable eager tracing of common animation objects.

Source/core/animation/AnimationPlayer.h

Index: Source/core/animation/AnimationPlayer.h
diff --git a/Source/core/animation/AnimationPlayer.h b/Source/core/animation/AnimationPlayer.h
index 5629ca483c066294dc82963f49bc11fe634e97f2..a6475aecb84ca47036f66a3231b3ca9376349e0b 100644
--- a/Source/core/animation/AnimationPlayer.h
+++ b/Source/core/animation/AnimationPlayer.h
@@ -34,6 +34,7 @@
 #include "core/animation/AnimationNode.h"
 #include "core/dom/ActiveDOMObject.h"
 #include "core/events/EventTarget.h"
+#include "platform/heap/Handle.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
@@ -41,6 +42,9 @@ namespace blink {
 class AnimationTimeline;
 class ExceptionState;
 
+class AnimationPlayer;
+WILL_BE_EAGERLY_TRACED(AnimationPlayer);
+
 class AnimationPlayer final : public RefCountedWillBeGarbageCollectedFinalized<AnimationPlayer>
     , public ActiveDOMObject
     , public EventTargetWithInlineData {
@@ -248,4 +252,4 @@ private:
 
 } // namespace blink
 
-#endif
+#endif // AnimationPlayer_h