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

chrome/browser/chromeos/login/session/stub_login_session_manager_delegate.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/session/stub_login_session_manager_delegate.h"
 
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/signin/signin_manager_factory.h"
 #include "chrome/common/pref_names.h"
 #include "components/signin/core/browser/signin_manager.h"
+#include "components/user_manager/user_id.h"
 
 namespace chromeos {
 
 StubLoginSessionManagerDelegate::StubLoginSessionManagerDelegate(
     Profile* profile,
-    const std::string& login_user_id)
+    const user_manager::UserID& login_user_id)
     : RestoreAfterCrashSessionManagerDelegate(profile, login_user_id) {
 }
 
 StubLoginSessionManagerDelegate::~StubLoginSessionManagerDelegate() {
 }
 
 void StubLoginSessionManagerDelegate::Start() {
   session_manager_->SetSessionState(session_manager::SESSION_STATE_ACTIVE);
 
   // For dev machines and stub user emulate as if sync has been initialized.
   SigninManagerFactory::GetForProfile(profile())
-      ->SetAuthenticatedAccountInfo(login_user_id(), login_user_id());
+      ->SetAuthenticatedAccountInfo(login_user_id().GetGaiaId(), login_user_id().GetUserEmail());
   RestoreAfterCrashSessionManagerDelegate::Start();
 }
 
 }  // namespace chromeos