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

components/safe_browsing_db/remote_database_manager.cc

 // Copyright 2015 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.
 
 #include "components/safe_browsing_db/remote_database_manager.h"
 
 #include <memory>
 #include <vector>
 
 #include "base/metrics/histogram_macros.h"
@@ skipping 81 matching lines @@
   // CancelCheck() will delete *this.
   db_manager_->CancelCheck(client_);
 }
 
 //
 // RemoteSafeBrowsingDatabaseManager methods
 //
 
 // 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);
 
   // The param is expected to be a comma-separated list of ints
   // corresponding to the enum types.  We're keeping this finch
   // control around so we can add back types if they later become dangerous.
   const std::string ints_str = variations::GetVariationParamValue(
       kAndroidFieldExperiment, kAndroidTypesToCheckParam);
   if (ints_str.empty()) {
@@ skipping 188 matching lines @@
   for (auto* req : to_callback) {
     DVLOG(1) << "Stopping: Invoking unfinished req for URL " << req->url();
     req->OnRequestDone(SB_THREAT_TYPE_SAFE, ThreatMetadata());
   }
   enabled_ = false;
 
   SafeBrowsingDatabaseManager::StopOnIOThread(shutdown);
 }
 
 }  // namespace safe_browsing