Use base::flat_set<> rather than std::set<> for ResourceType set

components/safe_browsing_db/remote_database_manager.cc

Index: components/safe_browsing_db/remote_database_manager.cc
diff --git a/components/safe_browsing_db/remote_database_manager.cc b/components/safe_browsing_db/remote_database_manager.cc
index 2def386d5f8b885838ebcc49de2cc136c07e5532..153a4dfb88b47907608d4c2a37a4e5c29fc9cdc1 100644
--- a/components/safe_browsing_db/remote_database_manager.cc
+++ b/components/safe_browsing_db/remote_database_manager.cc
@@ -99,6 +99,10 @@ void RemoteSafeBrowsingDatabaseManager::ClientRequest::OnRequestDone(
 
 // TODO(nparker): Add more tests for this class
 RemoteSafeBrowsingDatabaseManager::RemoteSafeBrowsingDatabaseManager() {
+  // Avoid memory allocations growing the underlying vector. Although this
+  // usually wastes a bit of memory, it will still be less than the default
+  // vector allocation strategy.
+  resource_types_to_check_.reserve(content::RESOURCE_TYPE_LAST_TYPE + 1);
   // Decide which resource types to check. These two are the minimum.
   resource_types_to_check_.insert(content::RESOURCE_TYPE_MAIN_FRAME);
   resource_types_to_check_.insert(content::RESOURCE_TYPE_SUB_FRAME);