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

chrome/browser/chromeos/login/saml/saml_offline_signin_limiter.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/saml/saml_offline_signin_limiter.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 27 matching lines @@
 }
 
 void SAMLOfflineSigninLimiter::SignedIn(UserContext::AuthFlow auth_flow) {
   PrefService* prefs = profile_->GetPrefs();
   const user_manager::User* user =
       ProfileHelper::Get()->GetUserByProfile(profile_);
   if (!user) {
     NOTREACHED();
     return;
   }
-  const std::string& user_id = user->email();
+  const user_manager::UserID& user_id = user->GetUserID();
 
   if (auth_flow == UserContext::AUTH_FLOW_GAIA_WITHOUT_SAML) {
     // The user went through online authentication and GAIA did not redirect to
     // a SAML IdP. No limit applies in this case. Clear the time of last login
     // with SAML and the flag enforcing online login, then return.
     prefs->ClearPref(prefs::kSAMLLastGAIASignInTime);
     user_manager::UserManager::Get()->SaveForceOnlineSignin(user_id, false);
     return;
   }
 
@@ skipping 78 matching lines @@
 }
 
 void SAMLOfflineSigninLimiter::ForceOnlineLogin() {
   const user_manager::User* user =
       ProfileHelper::Get()->GetUserByProfile(profile_);
   if (!user) {
     NOTREACHED();
     return;
   }
 
-  user_manager::UserManager::Get()->SaveForceOnlineSignin(user->email(), true);
-  RecordReauthReason(user->email(), ReauthReason::SAML_REAUTH_POLICY);
+  user_manager::UserManager::Get()->SaveForceOnlineSignin(user->GetUserID(), true);
+  RecordReauthReason(user->GetUserID(), ReauthReason::SAML_REAUTH_POLICY);
   offline_signin_limit_timer_.reset();
 }
 
 }  // namespace chromeos