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

chrome/browser/extensions/extension_management_test_util.cc

 // 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.
 
 #include "chrome/browser/extensions/extension_management_test_util.h"
 
 #include <string>
 
 #include "components/crx_file/id_util.h"
 #include "components/policy/core/common/configuration_policy_provider.h"
 #include "components/policy/core/common/mock_configuration_policy_provider.h"
 #include "components/policy/core/common/policy_bundle.h"
 #include "components/policy/core/common/policy_map.h"
 #include "components/policy/core/common/policy_namespace.h"
 #include "components/policy/core/common/policy_types.h"
 #include "policy/policy_constants.h"
 
 namespace extensions {
 
 namespace schema = schema_constants;
 
 namespace {
 
 const char kInstallSourcesPath[] = "*.install_sources";
 const char kAllowedTypesPath[] = "*.allowed_types";
 
-std::string make_path(std::string a, std::string b) {
+std::string make_path(const std::string& a, const std::string& b) {
   return a + "." + b;
 }
 
 }  // namespace
 
 ExtensionManagementPrefUpdaterBase::ExtensionManagementPrefUpdaterBase() {
 }
 
 ExtensionManagementPrefUpdaterBase::~ExtensionManagementPrefUpdaterBase() {
 }
@@ skipping 223 matching lines @@
 
 ExtensionManagementPolicyUpdater::~ExtensionManagementPolicyUpdater() {
   policies_->Get(policy::PolicyNamespace(policy::POLICY_DOMAIN_CHROME,
                                          std::string()))
       .Set(policy::key::kExtensionSettings, policy::POLICY_LEVEL_MANDATORY,
            policy::POLICY_SCOPE_USER, TakePref().release(), nullptr);
   provider_->UpdatePolicy(policies_.Pass());
 }
 
 }  // namespace extensions