Move FrameSink hierarchy registration to DisplayCompositor interface

cc/surfaces/compositor_frame_sink_support.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 CC_SURFACES_COMPOSITOR_FRAME_SINK_SUPPORT_H_
 #define CC_SURFACES_COMPOSITOR_FRAME_SINK_SUPPORT_H_
 
 #include <memory>
 #include <unordered_set>
 
@@ skipping 35 matching lines @@
     return reference_tracker_;
   }
 
   void EvictFrame();
   void SetNeedsBeginFrame(bool needs_begin_frame);
   void SubmitCompositorFrame(const LocalSurfaceId& local_surface_id,
                              CompositorFrame frame);
   void Require(const LocalSurfaceId& local_surface_id,
                const SurfaceSequence& sequence);
   void Satisfy(const SurfaceSequence& sequence);
-  void AddChildFrameSink(const FrameSinkId& child_frame_sink_id);
-  void RemoveChildFrameSink(const FrameSinkId& child_frame_sink_id);
   void RequestCopyOfSurface(std::unique_ptr<CopyOutputRequest> request);
   void ForceReclaimResources();
 
  private:
   // Update surface references with SurfaceManager for current CompositorFrame
   // that has |local_surface_id|. UpdateReferences() must be called on
   // |reference_tracker_| before calling this. Will add and remove top-level
   // root references if |display_| is not null.
   void UpdateSurfaceReferences(const SurfaceId& last_surface_id,
                                const LocalSurfaceId& local_surface_id);
@@ skipping 41 matching lines @@
   // Whether a request for begin frames has been issued.
   bool needs_begin_frame_ = false;
 
   // Whether or not a frame observer has been added.
   bool added_frame_observer_ = false;
 
   // Track the surface references for the surface corresponding to this
   // compositor frame sink.
   ReferencedSurfaceTracker reference_tracker_;
 
-  // The set of BeginFrame children of this CompositorFrameSink.
-  std::unordered_set<FrameSinkId, FrameSinkIdHash> child_frame_sinks_;
-
   const bool is_root_;
 
   // TODO(staraz): Remove this flag once ui::Compositor no longer needs to call
   // RegisterFrameSinkId().
   // A surfaceSequence's validity is bound to the lifetime of the parent
   // FrameSink that created it. We track the lifetime of FrameSinks through
   // RegisterFrameSinkId and InvalidateFrameSinkId. During startup and GPU
   // restart, a SurfaceSequence created by the top most layer compositor may be
   // used prior to the creation of the associated CompositorFrameSinkSupport.
   // CompositorFrameSinkSupport is created asynchronously when a new GPU channel
   // is established. Once we switch to SurfaceReferences, this ordering concern
   // goes away and we can remove this bool.
   const bool handles_frame_sink_id_invalidation_;
 
   base::WeakPtrFactory<CompositorFrameSinkSupport> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CompositorFrameSinkSupport);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_COMPOSITOR_FRAME_SINK_SUPPORT_H_