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

chrome/browser/chromeos/settings/cros_settings.cc

Index: chrome/browser/chromeos/settings/cros_settings.cc
diff --git a/chrome/browser/chromeos/settings/cros_settings.cc b/chrome/browser/chromeos/settings/cros_settings.cc
index 016b33a5ce0be0e84813a2d53273e96651a3d929..a8e00518d654d385e970a0691e21e4727bb14260 100644
--- a/chrome/browser/chromeos/settings/cros_settings.cc
+++ b/chrome/browser/chromeos/settings/cros_settings.cc
@@ -47,7 +47,7 @@ CrosSettings* CrosSettings::Get() {
 }
 
 // static
-bool CrosSettings::IsWhitelisted(const std::string& username,
+bool CrosSettings::IsWhitelisted(const user_manager::UserID& user_id,
                                  bool* wildcard_match) {
   // Skip whitelist check for tests.
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
@@ -60,7 +60,7 @@ bool CrosSettings::IsWhitelisted(const std::string& username,
   cros_settings->GetBoolean(kAccountsPrefAllowNewUser, &allow_new_user);
   if (allow_new_user)
     return true;
-  return cros_settings->FindEmailInList(kAccountsPrefUsers, username,
+  return cros_settings->FindEmailInList(kAccountsPrefUsers, user_id.GetUserEmail(),
                                         wildcard_match);
 }