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

chrome/browser/chromeos/login/supervised/supervised_user_login_flow.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/chromeos/login/supervised/supervised_user_login_flow.h"
 
 #include "base/base64.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 11 matching lines @@
 #include "chrome/common/chrome_switches.h"
 #include "chromeos/login/auth/key.h"
 #include "components/user_manager/user_manager.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
 
 namespace chromeos {
 
 SupervisedUserLoginFlow::SupervisedUserLoginFlow(
-    const std::string& user_id)
+    const user_manager::UserID& user_id)
     : ExtendedUserFlow(user_id),
       data_loaded_(false),
       weak_factory_(this) {
 }
 
 SupervisedUserLoginFlow::~SupervisedUserLoginFlow() {}
 
 void SupervisedUserLoginFlow::AppendAdditionalCommandLineSwitches() {
   user_manager::UserManager* user_manager = user_manager::UserManager::Get();
   if (user_manager->IsCurrentUserNew()) {
@@ skipping 59 matching lines @@
     const UserContext& login_context) {
   context_ = login_context;
 }
 
 void SupervisedUserLoginFlow::OnPasswordChangeDataLoaded(
     const base::DictionaryValue* password_data) {
   // Edge case, when manager has signed in and already updated the password.
   SupervisedUserAuthentication* auth =
       ChromeUserManager::Get()->GetSupervisedUserManager()->GetAuthentication();
   if (!auth->NeedPasswordChange(user_id(), password_data)) {
-    VLOG(1) << "Password already changed for " << user_id();
+    VLOG(1) << "Password already changed for " << user_id().GetUserEmail();
     auth->ClearScheduledPasswordUpdate(user_id());
     Finish();
     return;
   }
 
   // Two cases now - we can currently have either old-style password, or new
   // password.
   std::string base64_signature;
   std::string signature;
   std::string password;
@@ skipping 137 matching lines @@
 void SupervisedUserLoginFlow::LaunchExtraSteps(
     Profile* profile) {
   profile_ = profile;
   ChromeUserManager::Get()->GetSupervisedUserManager()->LoadSupervisedUserToken(
       profile,
       base::Bind(&SupervisedUserLoginFlow::OnSyncSetupDataLoaded,
                  weak_factory_.GetWeakPtr()));
 }
 
 }  // namespace chromeos