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

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

Index: chrome/browser/ui/webui/chromeos/login/supervised_user_creation_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/supervised_user_creation_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/supervised_user_creation_screen_handler.cc
index d533099ee9040f12b25dd35a600950a7f78dddeb..1ac8599c355bebb3fe9a215b02ad7747b080d13d 100644
--- a/chrome/browser/ui/webui/chromeos/login/supervised_user_creation_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/supervised_user_creation_screen_handler.cc
@@ -216,13 +216,14 @@ void SupervisedUserCreationScreenHandler::Show() {
   scoped_ptr<base::ListValue> users_list(new base::ListValue());
   const user_manager::UserList& users =
       ChromeUserManager::Get()->GetUsersAllowedForSupervisedUsersCreation();
-  std::string owner;
-  chromeos::CrosSettings::Get()->GetString(chromeos::kDeviceOwner, &owner);
+  std::string owner_email;
+  chromeos::CrosSettings::Get()->GetString(chromeos::kDeviceOwner, &owner_email);
+  const user_manager::UserID owner_id(user_manager::UserID::FromUserEmail(owner_email));
 
   for (user_manager::UserList::const_iterator it = users.begin();
        it != users.end();
        ++it) {
-    bool is_owner = ((*it)->email() == owner);
+    bool is_owner = ((*it)->GetUserID() == owner_id);
     base::DictionaryValue* user_dict = new base::DictionaryValue();
     UserSelectionScreen::FillUserDictionary(
         *it, is_owner, false, /* is_signin_to_add */
@@ -293,21 +294,21 @@ void SupervisedUserCreationScreenHandler::
 }
 
 void SupervisedUserCreationScreenHandler::HandleManagerSelected(
-    const std::string& manager_id) {
+    const std::string& manager_email) {
   if (!delegate_)
     return;
-  WallpaperManager::Get()->SetUserWallpaperNow(manager_id);
+  WallpaperManager::Get()->SetUserWallpaperNow(user_manager::UserID::FromUserEmail(manager_email));
 }
 
 void SupervisedUserCreationScreenHandler::HandleImportUserSelected(
-    const std::string& user_id) {
+    const std::string& user_email) {
   if (!delegate_)
     return;
 }
 
 void SupervisedUserCreationScreenHandler::HandleCheckSupervisedUserName(
     const base::string16& name) {
-  std::string user_id;
+  std::string user_email;
   if (NULL !=
       ChromeUserManager::Get()->GetSupervisedUserManager()->FindByDisplayName(
           base::CollapseWhitespace(name, true))) {
@@ -319,8 +320,8 @@ void SupervisedUserCreationScreenHandler::HandleCheckSupervisedUserName(
            l10n_util::GetStringUTF16(
                IDS_CREATE_SUPERVISED_USER_CREATE_ILLEGAL_USERNAME));
   } else if (delegate_ && delegate_->FindUserByDisplayName(
-                 base::CollapseWhitespace(name, true), &user_id)) {
-    CallJS("supervisedUserSuggestImport", name, user_id);
+                 base::CollapseWhitespace(name, true), &user_email)) {
+    CallJS("supervisedUserSuggestImport", name, user_email);
   } else {
     CallJS("supervisedUserNameOk", name);
   }
@@ -363,19 +364,19 @@ void SupervisedUserCreationScreenHandler::HandleCreateSupervisedUser(
 }
 
 void SupervisedUserCreationScreenHandler::HandleImportSupervisedUser(
-    const std::string& user_id) {
+    const std::string& user_email) {
   if (!delegate_)
     return;
 
   ShowStatusMessage(true /* progress */, l10n_util::GetStringUTF16(
       IDS_CREATE_SUPERVISED_USER_CREATION_CREATION_PROGRESS_MESSAGE));
 
-  delegate_->ImportSupervisedUser(user_id);
+  delegate_->ImportSupervisedUser(user_manager::UserID::FromUserEmail(user_email));
 }
 
 void SupervisedUserCreationScreenHandler::
     HandleImportSupervisedUserWithPassword(
-        const std::string& user_id,
+        const std::string& user_email,
         const std::string& password) {
   if (!delegate_)
     return;
@@ -383,7 +384,7 @@ void SupervisedUserCreationScreenHandler::
   ShowStatusMessage(true /* progress */, l10n_util::GetStringUTF16(
       IDS_CREATE_SUPERVISED_USER_CREATION_CREATION_PROGRESS_MESSAGE));
 
-  delegate_->ImportSupervisedUserWithPassword(user_id, password);
+  delegate_->ImportSupervisedUserWithPassword(user_manager::UserID::FromUserEmail(user_email), password);
 }
 
 void SupervisedUserCreationScreenHandler::HandleAuthenticateManager(
@@ -391,7 +392,7 @@ void SupervisedUserCreationScreenHandler::HandleAuthenticateManager(
     const std::string& manager_password) {
   const std::string manager_username =
       gaia::SanitizeEmail(raw_manager_username);
-  delegate_->AuthenticateManager(manager_username, manager_password);
+  delegate_->AuthenticateManager(user_manager::UserID::FromUserEmail(manager_username), manager_password);
 }
 
 // TODO(antrim) : this is an explicit code duplications with UserImageScreen.