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

chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc

Index: chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc
diff --git a/chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc b/chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc
index 2004ba38975656450cf6c0229d46932acab39db1..84312914d7027bf043703e8724f8176a16f4f103 100644
--- a/chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc
+++ b/chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc
@@ -117,7 +117,7 @@ class KioskProfileLoader::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),
@@ -157,8 +157,8 @@ void KioskProfileLoader::OnAuthSuccess(const UserContext& user_context) {
   // 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
@@ -170,7 +170,7 @@ 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();
 }
 
@@ -179,7 +179,7 @@ void KioskProfileLoader::PolicyLoadFailed() {
 }
 
 void KioskProfileLoader::OnOnlineChecked(
-    const std::string& email, bool success) {
+    const user_manager::UserID& user_id, bool success) {
   NOTREACHED();
 }