cc: Cleanup class/struct forward declarations

cc/trees/layer_tree_host_impl.h

 // Copyright 2011 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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <stddef.h>
 
 #include <bitset>
@@ skipping 33 matching lines @@
 #include "cc/trees/task_runner_provider.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace gfx {
 class ScrollOffset;
 }
 
 namespace cc {
 
 class BrowserControlsOffsetManager;
-class CompletionEvent;
 class CompositorFrameMetadata;
 class CompositorFrameSink;
 class DebugRectHistory;
 class EvictionTilePriorityQueue;
 class FrameRateCounter;
 class LayerImpl;
 class LayerTreeImpl;
 class MemoryHistory;
 class MutatorEvents;
 class MutatorHost;
 class PageScaleAnimation;
 class PendingTreeDurationHistogramTimer;
-class PictureLayerImpl;
 class RasterTilePriorityQueue;
-class TileTaskManager;
 class RasterBufferProvider;
-class RenderPassDrawQuad;
 class RenderingStatsInstrumentation;
 class ResourcePool;
 class ScrollElasticityHelper;
-class ScrollbarLayerImplBase;
 class SwapPromise;
 class SwapPromiseMonitor;
 class SynchronousTaskGraphRunner;
 class TaskGraphRunner;
-class TextureMailboxDeleter;
 class UIResourceBitmap;
-class UIResourceRequest;
 struct ScrollAndScaleSet;
 class Viewport;
 
 using BeginFrameCallbackList = std::vector<base::Closure>;
 
 enum class GpuRasterizationStatus {
   ON,
   ON_FORCED,
   OFF_DEVICE,
   OFF_VIEWPORT,
@@ skipping 733 matching lines @@
 
   std::unique_ptr<PendingTreeDurationHistogramTimer>
       pending_tree_duration_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_