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

chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h

Index: chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h
diff --git a/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h b/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h
index 98f959ca9287b06027e321ad654461045a387207..0625b97585d83d9cea7b5c727e879c20b1e1f57c 100644
--- a/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h
+++ b/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.h
@@ -16,6 +16,10 @@ namespace base {
 class FilePath;
 }
 
+namespace user_manager {
+class UserID;
+}
+
 namespace chromeos {
 
 // Class responsible for launching the demo app under a kiosk session.
@@ -26,12 +30,12 @@ class DemoAppLauncher : public KioskProfileLoader::Delegate {
 
   void StartDemoAppLaunch();
 
-  static bool IsDemoAppSession(const std::string& user_id);
+  static bool IsDemoAppSession(const user_manager::UserID& user_id);
   static void SetDemoAppPathForTesting(const base::FilePath& path);
 
-  static const char kDemoUserName[];
   static const char kDemoAppId[];
 
+  static user_manager::UserID GetDemoUserID();
  private:
   friend class DemoAppLauncherTest;