Add SurfaceManager option to use references exclusively.

cc/surfaces/surface_manager.h

 // Copyright 2014 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_SURFACE_MANAGER_H_
 #define CC_SURFACES_SURFACE_MANAGER_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 13 matching lines @@
 #include "cc/surfaces/surfaces_export.h"
 
 namespace cc {
 class BeginFrameSource;
 class CompositorFrame;
 class Surface;
 class SurfaceFactoryClient;
 
 class CC_SURFACES_EXPORT SurfaceManager : public SurfaceReferenceManager {
  public:
-  SurfaceManager();
+  enum class LifetimeType {
+    USE_REFERENCES,
+    USE_SEQUENCES,
+  };
+
+  explicit SurfaceManager(
+      LifetimeType lifetime_type = LifetimeType::USE_SEQUENCES);
   ~SurfaceManager() override;
 
   void RegisterSurface(Surface* surface);
   void DeregisterSurface(const SurfaceId& surface_id);
 
   // Destroy the Surface once a set of sequence numbers has been satisfied.
   void Destroy(std::unique_ptr<Surface> surface);
 
   Surface* GetSurfaceForId(const SurfaceId& surface_id);
 
@@ skipping 68 matching lines @@
  private:
   void RecursivelyAttachBeginFrameSource(const FrameSinkId& frame_sink_id,
                                          BeginFrameSource* source);
   void RecursivelyDetachBeginFrameSource(const FrameSinkId& frame_sink_id,
                                          BeginFrameSource* source);
   // Returns true if |child namespace| is or has |search_frame_sink_id| as a
   // child.
   bool ChildContains(const FrameSinkId& child_frame_sink_id,
                      const FrameSinkId& search_frame_sink_id) const;
 
+  // Garbage collects all destroyed surfaces not reachable from the root. Used
+  // when |use_references_| is true.
+  void GarbageCollectSurfacesFromRoot();
   void GarbageCollectSurfaces();
 
   // Removes reference from a parent surface to a child surface. Used to remove
   // references without triggered GC.
   void RemoveSurfaceReferenceImpl(const SurfaceId& parent_id,
                                   const SurfaceId& child_id);
 
+  // Use reference or sequence based lifetime management.
+  LifetimeType lifetime_type_;
+
   using SurfaceMap = std::unordered_map<SurfaceId, Surface*, SurfaceIdHash>;
   SurfaceMap surface_map_;
   base::ObserverList<SurfaceObserver> observer_list_;
   base::ThreadChecker thread_checker_;
 
   // List of surfaces to be destroyed, along with what sequences they're still
   // waiting on.
   using SurfaceDestroyList = std::list<std::unique_ptr<Surface>>;
   SurfaceDestroyList surfaces_to_destroy_;
 
@@ skipping 34 matching lines @@
   std::unordered_map<SurfaceId, SurfaceIdSet, SurfaceIdHash>
       parent_to_child_refs_;
 
   // Set of which sources are registered to which namespace.  Any child
   // that is implicitly using this namespace must be reachable by the
   // parent in the dag.
   std::unordered_map<BeginFrameSource*, FrameSinkId> registered_sources_;
 
   // Root SurfaceId that references display root surfaces. There is no Surface
   // with this id, it's for bookkeeping purposes only.
-  const SurfaceId kRootSurfaceId;
+  const SurfaceId root_surface_id_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_MANAGER_H_