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

chrome/browser/ui/ash/session_state_delegate_chromeos_unittest.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/session_state_delegate_chromeos.h"
 
 #include <string>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 63 matching lines @@
     // We must ensure that the PolicyCertVerifier outlives the
     // PolicyCertService so shutdown the profile here. Additionally, we need
     // to run the message loop between freeing the PolicyCertService and
     // freeing the PolicyCertVerifier (see
     // PolicyCertService::OnTrustAnchorsChanged() which is called from
     // PolicyCertService::Shutdown()).
     base::RunLoop().RunUntilIdle();
   }
 
   // Add and log in a user to the session.
-  void UserAddedToSession(std::string user) {
+  void UserAddedToSession(const std::string& user) {
     user_manager()->AddUser(user);
     user_manager()->LoginUser(user);
   }
 
   // Get the active user.
   const std::string& GetActiveUser() {
     return user_manager::UserManager::Get()->GetActiveUser()->email();
   }
 
   FakeChromeUserManager* user_manager() { return user_manager_; }
@@ skipping 188 matching lines @@
       prefs::kMultiProfileUserBehavior,
       chromeos::MultiProfileUserController::kBehaviorNotAllowed);
   user_manager()->AddUser("bb@b.b");
   EXPECT_FALSE(
       session_state_delegate()->CanAddUserToMultiProfile(&add_user_error));
   EXPECT_EQ(ash::SessionStateDelegate::ADD_USER_ERROR_NOT_ALLOWED_PRIMARY_USER,
             add_user_error);
 }
 
 }  // namespace chromeos