ui: Cleanup class/struct forward declarations

ui/compositor/layer.h

 // Copyright (c) 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 UI_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 15 matching lines @@
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkRegion.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/layer_animation_delegate.h"
 #include "ui/compositor/layer_delegate.h"
 #include "ui/compositor/layer_type.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/transform.h"
 
-class SkCanvas;
-
 namespace cc {
-class ContentLayer;
 class CopyOutputRequest;
 class Layer;
 class NinePatchLayer;
-class ResourceUpdateQueue;
 class SolidColorLayer;
 class SurfaceLayer;
 class TextureLayer;
 struct ReturnedResource;
 typedef std::vector<ReturnedResource> ReturnedResourceArray;
 }
 
 namespace ui {
 
 class Compositor;
@@ skipping 487 matching lines @@
   // The size of the frame or texture in DIP, set when SetShowDelegatedContent
   // or SetTextureMailbox was called.
   gfx::Size frame_size_in_dip_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_