Delete old RenderPassId mappings in SurfaceAggregator.

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 <map>
 #include <memory>
 #include <set>
 #include <unordered_map>
 #include <unordered_set>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/render_pass.h"
 #include "cc/resources/transferable_resource.h"
@@ skipping 37 matching lines @@
 
   struct PrewalkResult {
     PrewalkResult();
     ~PrewalkResult();
     // This is the set of Surfaces that were referenced by another Surface, but
     // not included in a SurfaceDrawQuad.
     std::set<SurfaceId> undrawn_surfaces;
     bool may_contain_video = false;
   };
 
+  struct RenderPassInfo {
+    // This is the id the pass is mapped to.
+    RenderPassId id;
+    // This is true if the pass was used in the last aggregated frame.
+    bool in_use = true;
+  };
+
   ClipData CalculateClipRect(const ClipData& surface_clip,
                              const ClipData& quad_clip,
                              const gfx::Transform& target_transform);
 
   RenderPassId RemapPassId(RenderPassId surface_local_pass_id,
                            const SurfaceId& surface_id);
 
   void HandleSurfaceQuad(const SurfaceDrawQuad* surface_quad,
                          const gfx::Transform& target_transform,
                          const ClipData& clip_rect,
@@ skipping 26 matching lines @@
   void PropagateCopyRequestPasses();
 
   int ChildIdForSurface(Surface* surface);
   gfx::Rect DamageRectForSurface(const Surface* surface,
                                  const RenderPass& source,
                                  const gfx::Rect& full_rect) const;
 
   SurfaceManager* manager_;
   ResourceProvider* provider_;
 
-  class RenderPassIdAllocator;
+  // Every Surface has its own RenderPass ID namespace. This structure maps
+  // each source RenderPassID to a unified ID namespace that's used in the
+  // aggregated frame. An entry is removed from the map if it's not used
+  // for one output frame.
   using RenderPassIdAllocatorMap =
-      std::unordered_map<SurfaceId,
-                         std::unique_ptr<RenderPassIdAllocator>,
-                         SurfaceIdHash>;
+      std::map<std::pair<SurfaceId, RenderPassId>, RenderPassInfo>;
   RenderPassIdAllocatorMap render_pass_allocator_map_;
   int next_render_pass_id_;
   const bool aggregate_only_damaged_;
   bool output_is_secure_;
 
   using SurfaceToResourceChildIdMap =
       std::unordered_map<SurfaceId, int, SurfaceIdHash>;
   SurfaceToResourceChildIdMap surface_id_to_resource_child_id_;
 
   // The following state is only valid for the duration of one Aggregate call
@@ skipping 42 matching lines @@
   TransferableResourceArray* dest_resource_list_;
 
   base::WeakPtrFactory<SurfaceAggregator> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceAggregator);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_AGGREGATOR_H_