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

chrome/browser/supervised_user/chromeos/manager_password_service_factory.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/supervised_user/chromeos/manager_password_service_factory.h"
 
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
 #include "chrome/browser/chromeos/login/users/supervised_user_manager.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
@@ skipping 29 matching lines @@
 
 ManagerPasswordServiceFactory::
     ~ManagerPasswordServiceFactory() {}
 
 KeyedService* ManagerPasswordServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {
   Profile* profile = static_cast<Profile*>(context);
   const user_manager::User* user =
       ProfileHelper::Get()->GetUserByProfile(profile);
   if (ChromeUserManager::Get()->GetSupervisedUserManager()->HasSupervisedUsers(
-          user->email())) {
+          user->GetUserID())) {
     ManagerPasswordService* result = new ManagerPasswordService();
     result->Init(
-        user->email(),
+        user->GetUserID(),
         SupervisedUserSyncServiceFactory::GetForProfile(profile),
         SupervisedUserSharedSettingsServiceFactory::GetForBrowserContext(
             profile));
     return result;
   }
   return NULL;
 }
 
 content::BrowserContext*
 ManagerPasswordServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }
 
 }  // namespace chromeos