Add cc::Surface ref counting.

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 48 matching lines @@
   // id namespace.
   void DidSatisfySequences(const FrameSinkId& frame_sink_id,
                            std::vector<uint32_t>* sequence);
 
   void RegisterFrameSinkId(const FrameSinkId& frame_sink_id);
 
   // Invalidate a frame_sink_id that might still have associated sequences,
   // possibly because a renderer process has crashed.
   void InvalidateFrameSinkId(const FrameSinkId& frame_sink_id);
 
+  // Adds a reference from a parent surface to a child surface. This signifies
+  // the parent surface is embedding the child surface and the child surface
+  // is needed until the reference is removed.
+  void AddSurfaceIdReference(const SurfaceId& parent_id,
+                             const SurfaceId& child_id);
+
+  // Removes a reference from a parent surface to a child surface. This signals
+  // the parent surface no longer needs the child surface.
+  void RemoveSurfaceIdReference(const SurfaceId& parent_id,
+                                const SurfaceId& child_id);
+
+  // Removes all references to and from surfaces that were created for
+  // |frame_sink_id|.
+  void RemoveAllReferencesForFrameSink(const FrameSinkId& frame_sink_id);
+
+  // Returns the number of surfaces that have references to |surface_id|. When
+  // the count is zero nothing is referencing the surface and it may be garbage
+  // collected.
+  int CountSurfaceReferences(const SurfaceId& surface_id) const;

[Fady Samuel, 2016/10/27 04:14:49]

nit: GetSurfaceReferenceCount?

[kylechar, 2016/10/27 21:14:10]

Done.

+
+  // Returns the number of surfaces that |surface_id| refers to.
+  int CountSurfaceReferees(const SurfaceId& surface_id) const;
+
   // SurfaceFactoryClient, hierarchy, and BeginFrameSource can be registered
   // and unregistered in any order with respect to each other.
   //
   // This happens in practice, e.g. the relationship to between ui::Compositor /
   // DelegatedFrameHost is known before ui::Compositor has a surface/client).
   // However, DelegatedFrameHost can register itself as a client before its
   // relationship with the ui::Compositor is known.
 
   // Associates a SurfaceFactoryClient with the surface id frame_sink_id it
   // uses.
@@ skipping 61 matching lines @@
     bool is_empty() const { return !client && children.empty(); }
     // The client that's responsible for creating this namespace.  Never null.
     SurfaceFactoryClient* client;
     // The currently assigned begin frame source for this client.
     BeginFrameSource* source;
     // This represents a dag of parent -> children mapping.
     std::vector<FrameSinkId> children;
   };
   std::unordered_map<FrameSinkId, FrameSinkSourceMapping, FrameSinkIdHash>
       frame_sink_source_map_;
+
+  using SurfaceIdSet = std::unordered_set<SurfaceId, SurfaceIdHash>;
+  // References from the child surface to parent surface. If there are zero
+  // entries in the set for a SurfaceId then nothing is referencing the surface
+  // and it can be garbage collected.
+  std::unordered_map<SurfaceId, SurfaceIdSet, SurfaceIdHash>
+      child_to_parent_refs_;
+  // References from the parent surface to child surface.
+  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_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_MANAGER_H_