blink: Cleanup class/struct forward declarations

third_party/WebKit/Source/platform/animation/CompositorAnimationHost.h

 // Copyright 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 CompositorAnimationHost_h
 #define CompositorAnimationHost_h
 
 #include "base/memory/ref_counted.h"
 #include "cc/animation/animation_host.h"
 #include "platform/PlatformExport.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "wtf/Noncopyable.h"
 
 #include <memory>
 
-namespace cc {
-struct ScrollOffsetAnimationUpdate;
-}
-
 namespace blink {
 
 // A compositor representation for cc::AnimationHost.
 // This class wraps cc::AnimationHost and is currently only created from
 // CompositorAnimationTimeline::compositorAnimationHost.
 // TODO(ymalik): Correctly introduce CompositorAnimationHost to blink. See
 // crbug.com/610763.
 class PLATFORM_EXPORT CompositorAnimationHost {
  public:
   explicit CompositorAnimationHost(cc::AnimationHost*);
 
   // TODO(ymalik): Remove when CompositorAnimationHost* optional nullable ptr
   // is returned. See crbug.com/610763.
   bool isNull() const;
 
   void adjustImplOnlyScrollOffsetAnimation(cc::ElementId,
                                            const gfx::Vector2dF& adjustment);
   void takeOverImplOnlyScrollOffsetAnimation(cc::ElementId);
 
  private:
   cc::AnimationHost* m_animationHost;
 };
 
 }  // namespace blink
 
 #endif  // CompositorAnimationTimeline_h