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

chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc

Index: chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
index e71da5ac5ad0c8feda8938ab4b068de21232d264..9aca4f46abf1f6ceab87d969e3c27996c1f7652a 100644
--- a/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/gaia_screen_handler.cc
@@ -504,8 +504,10 @@ void GaiaScreenHandler::HandleCompleteAuthentication(
   DCHECK(!gaia_id.empty());
   const std::string sanitized_email = gaia::SanitizeEmail(email);
   Delegate()->SetDisplayEmail(sanitized_email);
-  UserContext user_context(sanitized_email);
-  user_context.SetGaiaID(gaia_id);
+
+  user_manager::UserID user_id(user_manager::UserID::FromUserEmail(sanitized_email));
+  user_id.SetGaiaId(gaia_id);
+  UserContext user_context(user_id);
   user_context.SetKey(Key(password));
   user_context.SetAuthCode(auth_code);
   user_context.SetAuthFlow(using_saml
@@ -537,18 +539,18 @@ void GaiaScreenHandler::HandleCompleteLogin(const std::string& gaia_id,
   }
 
   // Consumer management enrollment is in progress.
-  const std::string owner_email =
-      user_manager::UserManager::Get()->GetOwnerEmail();
-  if (typed_email != owner_email) {
+  const user_manager::UserID owner_id =
+      user_manager::UserManager::Get()->GetOwnerID();
+  if (user_manager::UserID::FromUserEmail(typed_email) != owner_id) {
     // Show Gaia sign-in screen again, since we only allow the owner to sign
     // in.
-    populated_email_ = owner_email;
+    populated_email_ = owner_id.GetUserEmail();
     ShowGaiaAsync(is_enrolling_consumer_management_);
     return;
   }
 
   CHECK(consumer_management_);
-  consumer_management_->SetOwner(owner_email,
+  consumer_management_->SetOwner(owner_id,
                                  base::Bind(&GaiaScreenHandler::OnSetOwnerDone,
                                             weak_factory_.GetWeakPtr(),
                                             gaia_id,
@@ -664,8 +666,10 @@ void GaiaScreenHandler::DoCompleteLogin(const std::string& gaia_id,
   DCHECK(!gaia_id.empty());
   const std::string sanitized_email = gaia::SanitizeEmail(typed_email);
   Delegate()->SetDisplayEmail(sanitized_email);
-  UserContext user_context(sanitized_email);
-  user_context.SetGaiaID(gaia_id);
+
+  user_manager::UserID user_id(user_manager::UserID::FromUserEmail(sanitized_email));
+  user_id.SetGaiaId(gaia_id);
+  UserContext user_context(user_id);
   user_context.SetKey(Key(password));
   user_context.SetAuthFlow(using_saml
                                ? UserContext::AUTH_FLOW_GAIA_WITH_SAML
@@ -686,7 +690,7 @@ void GaiaScreenHandler::PopulateEmail(const std::string& user_id) {
   populated_email_ = user_id;
 }
 
-void GaiaScreenHandler::PasswordChangedFor(const std::string& user_id) {
+void GaiaScreenHandler::PasswordChangedFor(const user_manager::UserID& user_id) {
   password_changed_for_.insert(user_id);
 }
 
@@ -728,12 +732,12 @@ void GaiaScreenHandler::OnCookiesCleared(
   on_clear_callback.Run();
 }
 
-void GaiaScreenHandler::ShowSigninScreenForCreds(const std::string& username,
+void GaiaScreenHandler::ShowSigninScreenForCreds(const user_manager::UserID& user_id,
                                                  const std::string& password) {
-  VLOG(2) << "ShowSigninScreenForCreds  for user " << username
+  VLOG(2) << "ShowSigninScreenForCreds  for user " << user_id.GetUserEmail()
           << ", frame_state=" << frame_state();
 
-  test_user_ = username;
+  test_user_ = user_id.GetUserEmail();
   test_pass_ = password;
   test_expects_complete_login_ = true;
 
@@ -825,11 +829,13 @@ void GaiaScreenHandler::ShowGaiaScreenIfReady() {
     focus_stolen_ = false;
   }
 
-  // Note that LoadAuthExtension clears |populated_email_|.
-  if (populated_email_.empty())
+  const user_manager::UserID populated_user_id = user_manager::UserID::FromUserEmail(populated_email_);
+
+  // Note that LoadAuthExtension clears |populated_user_id|.
+  if (populated_user_id.empty())
     Delegate()->LoadSigninWallpaper();
   else
-    Delegate()->LoadWallpaper(populated_email_);
+    Delegate()->LoadWallpaper(populated_user_id);
 
   input_method::InputMethodManager* imm =
       input_method::InputMethodManager::Get();
@@ -839,14 +845,14 @@ void GaiaScreenHandler::ShowGaiaScreenIfReady() {
   imm->SetState(gaia_ime_state);
 
   // Set Least Recently Used input method for the user.
-  if (!populated_email_.empty()) {
-    SigninScreenHandler::SetUserInputMethod(populated_email_,
+  if (!populated_user_id.empty()) {
+    SigninScreenHandler::SetUserInputMethod(populated_user_id,
                                             gaia_ime_state.get());
   } else {
     std::vector<std::string> input_methods =
         imm->GetInputMethodUtil()->GetHardwareLoginInputMethodIds();
     const std::string owner_im = SigninScreenHandler::GetUserLRUInputMethod(
-        user_manager::UserManager::Get()->GetOwnerEmail());
+        user_manager::UserManager::Get()->GetOwnerID());
     const std::string system_im = g_browser_process->local_state()->GetString(
         language_prefs::kPreferredKeyboardLayout);
 
@@ -914,17 +920,19 @@ void GaiaScreenHandler::ShowWhitelistCheckFailedError() {
 void GaiaScreenHandler::LoadAuthExtension(bool force,
                                           bool silent_load,
                                           bool offline) {
+  const user_manager::UserID populated_user_id = user_manager::UserID::FromUserEmail(populated_email_);
+
   GaiaContext context;
   context.force_reload = force;
   context.is_local = offline;
-  context.password_changed = !populated_email_.empty() &&
-                             password_changed_for_.count(populated_email_);
+  context.password_changed = !populated_user_id.empty() &&
+                             password_changed_for_.count(populated_user_id);
   context.use_offline = offline;
-  context.email = populated_email_;
+  context.email = populated_user_id.GetUserEmail();
   context.is_enrolling_consumer_management = is_enrolling_consumer_management_;
 
   std::string gaia_id;
-  if (user_manager::UserManager::Get()->FindGaiaID(context.email, &gaia_id))
+  if (user_manager::UserManager::Get()->FindGaiaID(populated_user_id, &gaia_id))
     context.gaia_id = gaia_id;
 
   if (Delegate()) {