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

components/signin/core/browser/about_signin_internals.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 "components/signin/core/browser/about_signin_internals.h"
 
 #include "base/command_line.h"
 #include "base/hash.h"
 #include "base/i18n/time_formatting.h"
 #include "base/logging.h"
@@ skipping 325 matching lines @@
     const OAuth2TokenService::ScopeSet& scopes) {
   for (size_t i = 0; i < signin_status_.token_info_map[account_id].size();
        ++i) {
     TokenInfo* token = signin_status_.token_info_map[account_id][i];
     if (token->scopes == scopes)
       token->Invalidate();
   }
   NotifyObservers();
 }
 
-void AboutSigninInternals::OnRefreshTokenReceived(std::string status) {
+void AboutSigninInternals::OnRefreshTokenReceived(const std::string& status) {
   NotifySigninValueChanged(REFRESH_TOKEN_RECEIVED, status);
 }
 
-void AboutSigninInternals::OnAuthenticationResultReceived(std::string status) {
+void AboutSigninInternals::OnAuthenticationResultReceived(
+    const std::string& status) {
   NotifySigninValueChanged(AUTHENTICATION_RESULT_RECEIVED, status);
 }
 
 void AboutSigninInternals::OnErrorChanged() {
   NotifyObservers();
 }
 
 void AboutSigninInternals::GoogleSigninFailed(
     const GoogleServiceAuthError& error) {
   NotifyObservers();
@@ skipping 269 matching lines @@
   }
 
   for(const std::string& account_id : accounts_in_token_service) {
     base::DictionaryValue* entry = new base::DictionaryValue();
     entry->SetString("accountId", account_id);
     account_info->Append(entry);
   }
 
   return signin_status.Pass();
 }