Use flat_set for ResourceIdSet

cc/surfaces/surface_aggregator.cc

Index: cc/surfaces/surface_aggregator.cc
diff --git a/cc/surfaces/surface_aggregator.cc b/cc/surfaces/surface_aggregator.cc
index db1366da53cac0239eb0d95bb097ebc17893b0e7..a5e31ddc480f8a6f040c0b4cb7c8a3ac25e0ce35 100644
--- a/cc/surfaces/surface_aggregator.cc
+++ b/cc/surfaces/surface_aggregator.cc
@@ -617,7 +617,7 @@ gfx::Rect SurfaceAggregator::PrewalkTree(const SurfaceId& surface_id,
   }
   CHECK(debug_weak_this.get());
 
-  ResourceIdSet referenced_resources;
+  std::vector<ResourceId> referenced_resources;
   size_t reserve_size = frame.resource_list.size();
   referenced_resources.reserve(reserve_size);
 
@@ -701,7 +701,7 @@ gfx::Rect SurfaceAggregator::PrewalkTree(const SurfaceId& surface_id,
           invalid_frame = true;
           break;
         }
-        referenced_resources.insert(resource_id);
+        referenced_resources.push_back(resource_id);
       }
     }
   }
@@ -711,8 +711,10 @@ gfx::Rect SurfaceAggregator::PrewalkTree(const SurfaceId& surface_id,
   CHECK(debug_weak_this.get());
   valid_surfaces_.insert(surface->surface_id());
 
+  ResourceIdSet resource_set(std::move(referenced_resources),
+                             base::KEEP_FIRST_OF_DUPES);
   if (provider_)
-    provider_->DeclareUsedResourcesFromChild(child_id, referenced_resources);
+    provider_->DeclareUsedResourcesFromChild(child_id, resource_set);
   CHECK(debug_weak_this.get());
 
   gfx::Rect damage_rect;