Remove parts of //cc we aren't using

cc/animation/layer_animation_event_observer.h

-// Copyright 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CC_ANIMATION_LAYER_ANIMATION_EVENT_OBSERVER_H_
-#define CC_ANIMATION_LAYER_ANIMATION_EVENT_OBSERVER_H_
-
-#include "cc/base/cc_export.h"
-
-namespace cc {
-
-struct AnimationEvent;
-
-class CC_EXPORT LayerAnimationEventObserver {
- public:
-  virtual void OnAnimationStarted(const AnimationEvent& event) = 0;
-
- protected:
-  virtual ~LayerAnimationEventObserver() {}
-};
-
-}  // namespace cc
-
-#endif  // CC_ANIMATION_LAYER_ANIMATION_EVENT_OBSERVER_H_
-