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

chrome/browser/chromeos/login/app_launch_signin_screen.cc

Index: chrome/browser/chromeos/login/app_launch_signin_screen.cc
diff --git a/chrome/browser/chromeos/login/app_launch_signin_screen.cc b/chrome/browser/chromeos/login/app_launch_signin_screen.cc
index e13afed32ea55c3087c40b1e8ba8e5a0f0dc9ce9..8ac286469f265934e4df24790f716cbc72c321cd 100644
--- a/chrome/browser/chromeos/login/app_launch_signin_screen.cc
+++ b/chrome/browser/chromeos/login/app_launch_signin_screen.cc
@@ -42,7 +42,7 @@ void AppLaunchSigninScreen::Show() {
 
 void AppLaunchSigninScreen::InitOwnerUserList() {
   user_manager::UserManager* user_manager = GetUserManager();
-  const std::string& owner_email = user_manager->GetOwnerEmail();
+  const user_manager::UserID& owner_id = user_manager->GetOwnerID();
   const user_manager::UserList& all_users = user_manager->GetUsers();
 
   owner_user_list_.clear();
@@ -50,7 +50,7 @@ void AppLaunchSigninScreen::InitOwnerUserList() {
        it != all_users.end();
        ++it) {
     user_manager::User* user = *it;
-    if (user->email() == owner_email) {
+    if (user->GetUserID() == owner_id) {

[Denis Kuznetsov (DE-MUC), 2015/06/10 16:50:46]

We should think about == contract for UserID, like, if one userid is (GaiaID,
someone@gmail.com) and second one is ("", someone@gmail.com) should be they
treated as same or not?
Maybe we should keep == for field-by-field equality, and have separate method
bool matches(UserID other) for "equal, even though one of elements can be
incomplete", ?

       owner_user_list_.push_back(user);
       break;
     }
@@ -100,7 +100,7 @@ void AppLaunchSigninScreen::MigrateUserData(const std::string& old_password) {
   NOTREACHED();
 }
 
-void AppLaunchSigninScreen::LoadWallpaper(const std::string& username) {
+void AppLaunchSigninScreen::LoadWallpaper(const user_manager::UserID& user_id) {
 }
 
 void AppLaunchSigninScreen::LoadSigninWallpaper() {
@@ -109,7 +109,7 @@ void AppLaunchSigninScreen::LoadSigninWallpaper() {
 void AppLaunchSigninScreen::OnSigninScreenReady() {
 }
 
-void AppLaunchSigninScreen::RemoveUser(const std::string& username) {
+void AppLaunchSigninScreen::RemoveUser(const user_manager::UserID& user_id) {
   NOTREACHED();
 }
 
@@ -143,7 +143,7 @@ void AppLaunchSigninScreen::SetWebUIHandler(
 }
 
 void AppLaunchSigninScreen::ShowSigninScreenForCreds(
-    const std::string& username,
+    const user_manager::UserID& user_id,
     const std::string& password) {
   NOTREACHED();
 }
@@ -217,7 +217,7 @@ void AppLaunchSigninScreen::HandleGetUsers() {
   webui_handler_->LoadUsers(users_list, false);
 }
 
-void AppLaunchSigninScreen::CheckUserStatus(const std::string& user_id) {
+void AppLaunchSigninScreen::CheckUserStatus(const user_manager::UserID& user_id) {
 }
 
 }  // namespace chromeos