Cleanup: Pass std::string as const reference if possible

components/sync_driver/device_info.cc

 // Copyright (c) 2012 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 "base/values.h"
 #include "components/sync_driver/device_info.h"
 
 namespace sync_driver {
 
 DeviceInfo::DeviceInfo(const std::string& guid,
@@ skipping 88 matching lines @@
 base::DictionaryValue* DeviceInfo::ToValue() {
   base::DictionaryValue* value = new base::DictionaryValue();
   value->SetString("name", client_name_);
   value->SetString("id", public_id_);
   value->SetString("os", GetOSString());
   value->SetString("type", GetDeviceTypeString());
   value->SetString("chromeVersion", chrome_version_);
   return value;
 }
 
-void DeviceInfo::set_public_id(std::string id) {
+void DeviceInfo::set_public_id(const std::string& id) {
   public_id_ = id;
 }
 
 }  // namespace sync_driver