Reduce SurfaceIdAllocator usage and tie SurfaceFactory to a single FrameSinkId

ui/compositor/compositor.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_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 366 matching lines @@
   void SetOutputIsSecure(bool output_is_secure);
 
   const cc::LayerTreeDebugState& GetLayerTreeDebugState() const;
   void SetLayerTreeDebugState(const cc::LayerTreeDebugState& debug_state);
   const cc::RendererSettings& GetRendererSettings() const;
 
   LayerAnimatorCollection* layer_animator_collection() {
     return &layer_animator_collection_;
   }
 
-  cc::SurfaceIdAllocator* surface_id_allocator() {
-    return surface_id_allocator_.get();
-  }
+  const cc::FrameSinkId& frame_sink_id() const { return frame_sink_id_; }
 
  private:
   friend class base::RefCounted<Compositor>;
   friend class CompositorLock;
 
   // Called by CompositorLock.
   void UnlockCompositor();
 
   // Called to release any pending CompositorLock
   void CancelCompositorLock();
 
   gfx::Size size_;
 
   ui::ContextFactory* context_factory_;
 
   // The root of the Layer tree drawn by this compositor.
   Layer* root_layer_;
 
   base::ObserverList<CompositorObserver, true> observer_list_;
   base::ObserverList<CompositorAnimationObserver> animation_observer_list_;
 
   gfx::AcceleratedWidget widget_;
 #if defined(USE_AURA)
   ui::Window* window_;
 #endif
   // A map from child id to parent id.
-  std::unordered_map<cc::FrameSinkId, cc::FrameSinkId, cc::FrameSinkIdHash>
-      frame_sinks_;
+  std::unordered_set<cc::FrameSinkId, cc::FrameSinkIdHash> child_frame_sinks_;
   bool widget_valid_;
   bool compositor_frame_sink_requested_;
+  const cc::FrameSinkId frame_sink_id_;
   std::unique_ptr<cc::SurfaceIdAllocator> surface_id_allocator_;
   scoped_refptr<cc::Layer> root_web_layer_;
   std::unique_ptr<cc::LayerTreeHost> host_;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   // The manager of vsync parameters for this compositor.
   scoped_refptr<CompositorVSyncManager> vsync_manager_;
 
   // The device scale factor of the monitor that this compositor is compositing
   // layers on.
   float device_scale_factor_;
 
   bool locks_will_time_out_;
   CompositorLock* compositor_lock_;
 
   LayerAnimatorCollection layer_animator_collection_;
   scoped_refptr<cc::AnimationTimeline> animation_timeline_;
 
   gfx::ColorSpace color_space_;
 
   base::WeakPtrFactory<Compositor> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_