We should use UserID object to identify users instead of username.

chrome/browser/ui/views/frame/system_menu_model_builder.cc

 // Copyright (c) 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/views/frame/system_menu_model_builder.h"
 
 #include "base/command_line.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/ui/browser_commands.h"
@@ skipping 151 matching lines @@
   ash::SessionStateDelegate* delegate =
       ash::Shell::GetInstance()->session_state_delegate();
   int logged_in_users = delegate->NumberOfLoggedInUsers();
   if (logged_in_users <= 1)
     return;
 
   // If this does not belong to a profile or there is no window, or the window
   // is not owned by anyone, we don't show the menu addition.
   chrome::MultiUserWindowManager* manager =
       chrome::MultiUserWindowManager::GetInstance();
-  const std::string user_id =
+  const user_manager::UserID user_id =
       multi_user_util::GetUserIDFromProfile(browser()->profile());
   aura::Window* window = browser()->window()->GetNativeWindow();
   if (user_id.empty() || !window || manager->GetWindowOwner(window).empty())
     return;
 
   model->AddSeparator(ui::NORMAL_SEPARATOR);
   DCHECK(logged_in_users <= 3);
   for (int user_index = 1; user_index < logged_in_users; ++user_index) {
     const user_manager::UserInfo* user_info = delegate->GetUserInfo(user_index);
     model->AddItem(
         user_index == 1 ? IDC_VISIT_DESKTOP_OF_LRU_USER_2
                         : IDC_VISIT_DESKTOP_OF_LRU_USER_3,
         l10n_util::GetStringFUTF16(IDS_VISIT_DESKTOP_OF_LRU_USER,
                                    user_info->GetDisplayName(),
                                    base::ASCIIToUTF16(user_info->GetEmail())));
   }
 #endif
 }