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

chrome/browser/ui/ash/multi_user/multi_user_context_menu_chromeos.cc

 // Copyright 2013 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/ui/ash/multi_user/multi_user_context_menu.h"
 
 #include "ash/multi_profile_uma.h"
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
 #include "base/bind.h"
@@ skipping 77 matching lines @@
                                     : IDC_VISIT_DESKTOP_OF_LRU_USER_3,
                     l10n_util::GetStringFUTF16(
                         IDS_VISIT_DESKTOP_OF_LRU_USER,
                         user_info->GetDisplayName(),
                         base::ASCIIToUTF16(user_info->GetEmail())));
     }
   }
   return model.Pass();
 }
 
-void OnAcceptTeleportWarning(
-    const std::string user_id, aura::Window* window_, bool no_show_again) {
+void OnAcceptTeleportWarning(const std::string& user_id,
+                             aura::Window* window_,
+                             bool no_show_again) {
   PrefService* pref = ProfileManager::GetActiveUserProfile()->GetPrefs();
   pref->SetBoolean(prefs::kMultiProfileWarningShowDismissed, no_show_again);
 
   ash::MultiProfileUMA::RecordTeleportAction(
       ash::MultiProfileUMA::TELEPORT_WINDOW_CAPTION_MENU);
 
   chrome::MultiUserWindowManager::GetInstance()->ShowWindowForUser(window_,
                                                                    user_id);
 }
 
@@ skipping 29 matching lines @@
           return;
         }
       }
       chromeos::ShowMultiprofilesWarningDialog(on_accept);
       return;
     }
     default:
       NOTREACHED();
   }
 }