How to enable Internationalization of login form with custom theme in my Realm

Issue

• I have custom theme which has type login only and want to use it in my Realm.
  After enabling the Internationalization at Themes tab of my Realm, it shows the combo at login page, but no other languages are shown, excepting the English(en). How can I add locale Portuguese (brazil) to it?

• I want to enable Internationalization of my Realm with custom theme.
  According to document. I added translated message as themes/mytheme/login/messages/messages_pt_BR.properties and the locale to parameter locales in my theme.properties. But in Admin Console, only en(English) is available in Supported Locales field in Theme tab even after enabling Internationalization like the following.