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

chrome/browser/ui/startup/startup_browser_creator.cc

Index: chrome/browser/ui/startup/startup_browser_creator.cc
diff --git a/chrome/browser/ui/startup/startup_browser_creator.cc b/chrome/browser/ui/startup/startup_browser_creator.cc
index 82f182bb39d5ad8258840ca0900d60f37575a454..28a1bdb06ffa3c433e2bdd3afd9fb953121653f8 100644
--- a/chrome/browser/ui/startup/startup_browser_creator.cc
+++ b/chrome/browser/ui/startup/startup_browser_creator.cc
@@ -63,6 +63,7 @@
 #include "components/search_engines/util.h"
 #include "components/signin/core/common/profile_management_switches.h"
 #include "components/url_fixer/url_fixer.h"
+#include "components/user_manager/user_id.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/child_process_security_policy.h"
 #include "content/public/browser/navigation_controller.h"
@@ -572,7 +573,7 @@ bool StartupBrowserCreator::ProcessCmdLineImpl(
   // possible. We should instead cleanly exit and go back to the OOBE screen,
   // where we will launch again after the timeout has expired.
   if (chromeos::DemoAppLauncher::IsDemoAppSession(
-      command_line.GetSwitchValueASCII(chromeos::switches::kLoginUser))) {
+      user_manager::UserID::FromUserEmail(command_line.GetSwitchValueASCII(chromeos::switches::kLoginUser)))) {
     chrome::AttemptUserExit();
     return false;
   }
@@ -822,7 +823,7 @@ void StartupBrowserCreator::ProcessCommandLineAlreadyRunning(
     profile_manager->CreateProfileAsync(profile_path,
         base::Bind(&StartupBrowserCreator::ProcessCommandLineOnProfileCreated,
                    command_line, cur_dir), base::string16(), base::string16(),
-                   std::string());
+                   user_manager::UserID(std::string(), std::string()));
     return;
   }