cc: Cleanup class/struct forward declarations

cc/animation/scroll_offset_animations_impl.h

 // Copyright (c) 2016 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_SCROLL_OFFSET_ANIMATIONS_IMPL_H_
 #define CC_ANIMATION_SCROLL_OFFSET_ANIMATIONS_IMPL_H_
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
 #include "cc/animation/animation_delegate.h"
 #include "cc/animation/scroll_offset_animation_curve.h"
 #include "cc/trees/mutator_host_client.h"
 #include "ui/gfx/geometry/scroll_offset.h"
 
 namespace cc {
 
 class AnimationPlayer;
 class AnimationHost;
 class AnimationTimeline;
-class ElementAnimations;
 
 // Contains an AnimationTimeline and its AnimationPlayer that owns the impl
 // only scroll offset animations running on a particular CC Layer.
 // We have just one player for impl-only scroll offset animations. I.e. only
 // one element can have an impl-only scroll offset animation at any given time.
 // Note that this class only exists on the compositor thread.
 class CC_EXPORT ScrollOffsetAnimationsImpl : public AnimationDelegate {
  public:
   explicit ScrollOffsetAnimationsImpl(AnimationHost* animation_host);
 
@@ skipping 43 matching lines @@
   // I.e. only one element can have an impl-only scroll offset animation at
   // any given time.
   scoped_refptr<AnimationPlayer> scroll_offset_animation_player_;
 
   DISALLOW_COPY_AND_ASSIGN(ScrollOffsetAnimationsImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_SCROLL_OFFSET_ANIMATIONS_IMPL_H_