cc: Simplify Task and its derived classes.

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 <memory>
@@ skipping 56 matching lines @@
 class RasterTilePriorityQueue;
 class TileTaskWorkerPool;
 class RenderPassDrawQuad;
 class RenderingStatsInstrumentation;
 class ResourcePool;
 class ScrollElasticityHelper;
 class ScrollbarLayerImplBase;
 class SwapPromise;
 class SwapPromiseMonitor;
 class SynchronousTaskGraphRunner;
+class TaskGraphRunner;
 class TextureMailboxDeleter;
 class TopControlsManager;
 class UIResourceBitmap;
 class UIResourceRequest;
 struct ScrollAndScaleSet;
 class Viewport;
 
 using BeginFrameCallbackList = std::vector<base::Closure>;
 
 enum class GpuRasterizationStatus {
@@ skipping 783 matching lines @@
   std::unique_ptr<Viewport> viewport_;
 
   LayerTreeMutator* mutator_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_