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

chrome/browser/chromeos/settings/cros_settings.cc

 // Copyright (c) 2012 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/settings/cros_settings.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/stl_util.h"
@@ skipping 29 matching lines @@
   g_cros_settings = NULL;
 }
 
 // static
 CrosSettings* CrosSettings::Get() {
   CHECK(g_cros_settings);
   return g_cros_settings;
 }
 
 // static
-bool CrosSettings::IsWhitelisted(const std::string& username,
+bool CrosSettings::IsWhitelisted(const user_manager::UserID& user_id,
                                  bool* wildcard_match) {
   // Skip whitelist check for tests.
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           chromeos::switches::kOobeSkipPostLogin)) {
     return true;
   }
 
   CrosSettings* cros_settings = CrosSettings::Get();
   bool allow_new_user = false;
   cros_settings->GetBoolean(kAccountsPrefAllowNewUser, &allow_new_user);
   if (allow_new_user)
     return true;
-  return cros_settings->FindEmailInList(kAccountsPrefUsers, username,
+  return cros_settings->FindEmailInList(kAccountsPrefUsers, user_id.GetUserEmail(),
                                         wildcard_match);
 }
 
 CrosSettings::CrosSettings(DeviceSettingsService* device_settings_service) {
   CrosSettingsProvider::NotifyObserversCallback notify_cb(
       base::Bind(&CrosSettings::FireObservers,
                  // This is safe since |this| is never deleted.
                  base::Unretained(this)));
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kStubCrosSettings)) {
@@ skipping 266 matching lines @@
 
 ScopedTestCrosSettings::ScopedTestCrosSettings() {
   CrosSettings::Initialize();
 }
 
 ScopedTestCrosSettings::~ScopedTestCrosSettings() {
   CrosSettings::Shutdown();
 }
 
 }  // namespace chromeos