Reusing base::IdType<...> to implement SurfaceId.

cc/surfaces/surface_aggregator.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_AGGREGATOR_H_
 #define CC_SURFACES_SURFACE_AGGREGATOR_H_
 
 #include <set>
 #include <unordered_map>
 #include <unordered_set>
@@ skipping 18 matching lines @@
 class CC_SURFACES_EXPORT SurfaceAggregatorClient {
  public:
   virtual ~SurfaceAggregatorClient() {}
 
   virtual void AddSurface(Surface* surface) = 0;
   virtual void RemoveSurface(Surface* surface) = 0;
 };
 
 class CC_SURFACES_EXPORT SurfaceAggregator {
  public:
-  using SurfaceIndexMap = std::unordered_map<SurfaceId, int, SurfaceIdHash>;
+  using SurfaceIndexMap = std::unordered_map<SurfaceId, int, SurfaceId::Hasher>;
 
   SurfaceAggregator(SurfaceAggregatorClient* client,
                     SurfaceManager* manager,
                     ResourceProvider* provider,
                     bool aggregate_only_damaged);
   ~SurfaceAggregator();
 
   scoped_ptr<CompositorFrame> Aggregate(SurfaceId surface_id);
   void ReleaseResources(SurfaceId surface_id);
   SurfaceIndexMap& previous_contained_surfaces() {
@@ skipping 59 matching lines @@
                                  const gfx::Rect& full_rect) const;
 
   SurfaceAggregatorClient* client_;  // Outlives this class.
   SurfaceManager* manager_;
   ResourceProvider* provider_;
 
   class RenderPassIdAllocator;
   using RenderPassIdAllocatorMap =
       std::unordered_map<SurfaceId,
                          scoped_ptr<RenderPassIdAllocator>,
-                         SurfaceIdHash>;
+                         SurfaceId::Hasher>;
   RenderPassIdAllocatorMap render_pass_allocator_map_;
   int next_render_pass_id_;
   const bool aggregate_only_damaged_;
 
   using SurfaceToResourceChildIdMap =
-      std::unordered_map<SurfaceId, int, SurfaceIdHash>;
+      std::unordered_map<SurfaceId, int, SurfaceId::Hasher>;
   SurfaceToResourceChildIdMap surface_id_to_resource_child_id_;
 
   // The following state is only valid for the duration of one Aggregate call
   // and is only stored on the class to avoid having to pass through every
   // function call.
 
   // This is the set of surfaces referenced in the aggregation so far, used to
   // detect cycles.
   using SurfaceSet = std::set<SurfaceId>;
   SurfaceSet referenced_surfaces_;
 
   // For each Surface used in the last aggregation, gives the frame_index at
   // that time.
   SurfaceIndexMap previous_contained_surfaces_;
   SurfaceIndexMap contained_surfaces_;
 
   // After surface validation, every Surface in this set is valid.
-  std::unordered_set<SurfaceId, SurfaceIdHash> valid_surfaces_;
+  std::unordered_set<SurfaceId, SurfaceId::Hasher> valid_surfaces_;
 
   // This is the pass list for the aggregated frame.
   RenderPassList* dest_pass_list_;
 
   // The root damage rect of the currently-aggregating frame.
   gfx::Rect root_damage_rect_;
 
   // True if the frame that's currently being aggregated has copy requests.
   // This is valid during Aggregate after PrewalkTree is called.
   bool has_copy_requests_;
 
   // Resource list for the aggregated frame.
   TransferableResourceArray* dest_resource_list_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceAggregator);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_AGGREGATOR_H_