ElementAnimations should hold an ObservableList of AnimationPlayers.

cc/animation/animation_player.h

Index: cc/animation/animation_player.h
diff --git a/cc/animation/animation_player.h b/cc/animation/animation_player.h
index 247b24c3d23c5fcc7ec66bedd5c2c0a70519d0db..5c4c58e94db4c7fdf3ed8f220b668a02b29b8fe7 100644
--- a/cc/animation/animation_player.h
+++ b/cc/animation/animation_player.h
@@ -7,7 +7,6 @@
 
 #include <vector>
 
-#include "base/containers/linked_list.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
@@ -31,8 +30,7 @@ class ElementAnimations;
 // same-property animations.
 // Each AnimationPlayer has its copy on the impl thread.
 // This is a CC counterpart for blink::AnimationPlayer (in 1:1 relationship).
-class CC_EXPORT AnimationPlayer : public base::RefCounted<AnimationPlayer>,
-                                  public base::LinkNode<AnimationPlayer> {
+class CC_EXPORT AnimationPlayer : public base::RefCounted<AnimationPlayer> {
  public:
   static scoped_refptr<AnimationPlayer> Create(int id);
   scoped_refptr<AnimationPlayer> CreateImplInstance() const;