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

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

Index: chrome/browser/chromeos/login/demo_mode/demo_app_launcher.cc
diff --git a/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.cc b/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.cc
index 6be11b895d9e117c323bd0ae6afa70ac9287a08e..d6c2d16e958b33d7b4e9f7e86bd542a5450c53d5 100644
--- a/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.cc
+++ b/chrome/browser/chromeos/login/demo_mode/demo_app_launcher.cc
@@ -27,9 +27,12 @@
 #include "extensions/common/extension.h"
 #include "ui/base/window_open_disposition.h"
 
+namespace {
+const char kDemoUserName[] = "demouser@demo.app.local";
+}
+
 namespace chromeos {
 
-const char DemoAppLauncher::kDemoUserName[] = "demouser@demo.app.local";
 const char DemoAppLauncher::kDemoAppId[] = "klimoghijjogocdbaikffefjfcfheiel";
 const base::FilePath::CharType kDefaultDemoAppPath[] =
     FILE_PATH_LITERAL("/usr/share/chromeos-assets/demo_app");
@@ -50,13 +53,13 @@ void DemoAppLauncher::StartDemoAppLaunch() {
   DVLOG(1) << "Launching demo app...";
   // user_id = DemoAppUserId, force_emphemeral = true, delegate = this.
   kiosk_profile_loader_.reset(
-      new KioskProfileLoader(kDemoUserName, true, this));
+      new KioskProfileLoader(GetDemoUserID(), true, this));
   kiosk_profile_loader_->Start();
 }
 
 // static
-bool DemoAppLauncher::IsDemoAppSession(const std::string& user_id) {
-  return user_id == kDemoUserName;
+bool DemoAppLauncher::IsDemoAppSession(const user_manager::UserID& user_id) {
+  return user_id == GetDemoUserID();
 }
 
 // static
@@ -65,6 +68,11 @@ void DemoAppLauncher::SetDemoAppPathForTesting(const base::FilePath& path) {
   demo_app_path_ = new base::FilePath(path);
 }
 
+// static
+user_manager::UserID DemoAppLauncher::GetDemoUserID() {
+  return user_manager::UserID::FromUserEmail(kDemoUserName);
+}
+
 void DemoAppLauncher::OnProfileLoaded(Profile* profile) {
   DVLOG(1) << "Profile loaded... Starting demo app launch.";