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

chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc

 // Copyright 2013 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/app_mode/kiosk_profile_loader.h"
 
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
@@ skipping 99 matching lines @@
   KioskProfileLoader* loader_;
   int retry_count_;
 
   DISALLOW_COPY_AND_ASSIGN(CryptohomedChecker);
 };
 
 
 ////////////////////////////////////////////////////////////////////////////////
 // KioskProfileLoader
 
-KioskProfileLoader::KioskProfileLoader(const std::string& app_user_id,
+KioskProfileLoader::KioskProfileLoader(const user_manager::UserID& app_user_id,
                                        bool use_guest_mount,
                                        Delegate* delegate)
     : user_id_(app_user_id),
       use_guest_mount_(use_guest_mount),
       delegate_(delegate) {}
 
 KioskProfileLoader::~KioskProfileLoader() {}
 
 void KioskProfileLoader::Start() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
@@ skipping 19 matching lines @@
   // LoginPerformer will delete itself.
   login_performer_->set_delegate(NULL);
   ignore_result(login_performer_.release());
 
   // If we are launching a demo session, we need to start MountGuest with the
   // guest username; this is because there are several places in the cros code
   // which rely on the username sent to cryptohome to be $guest. Back in Chrome
   // we switch this back to the demo user name to correctly identify this
   // user as a demo user.
   UserContext context = user_context;
-  if (context.GetUserID() == chromeos::login::kGuestUserName)
-    context.SetUserID(DemoAppLauncher::kDemoUserName);
+  if (context.GetUserID() == chromeos::login::GetGuestUserID())
+    context.SetUserID(DemoAppLauncher::GetDemoUserID());
   UserSessionManager::GetInstance()->StartSession(
       context, UserSessionManager::PRIMARY_USER_SESSION,
       false,  // has_auth_cookies
       false,  // Start session for user.
       this);
 }
 
 void KioskProfileLoader::OnAuthFailure(const AuthFailure& error) {
   ReportLaunchResult(LoginFailureToKioskAppLaunchError(error));
 }
 
-void KioskProfileLoader::WhiteListCheckFailed(const std::string& email) {
+void KioskProfileLoader::WhiteListCheckFailed(const user_manager::UserID& user_id) {
   NOTREACHED();
 }
 
 void KioskProfileLoader::PolicyLoadFailed() {
   ReportLaunchResult(KioskAppLaunchError::POLICY_LOAD_FAILED);
 }
 
 void KioskProfileLoader::OnOnlineChecked(
-    const std::string& email, bool success) {
+    const user_manager::UserID& user_id, bool success) {
   NOTREACHED();
 }
 
 void KioskProfileLoader::OnProfilePrepared(Profile* profile,
                                            bool browser_launched) {
   // This object could be deleted any time after successfully reporting
   // a profile load, so invalidate the delegate now.
   UserSessionManager::GetInstance()->DelegateDeleted(this);
 
   delegate_->OnProfileLoaded(profile);
   ReportLaunchResult(KioskAppLaunchError::NONE);
 }
 
 }  // namespace chromeos