Hi Coery,
  ``app_install_manager`` also call ``KeyboardHelper.setLayoutEnabled``, so if you do not want to call  ``KeyboardHelper.saveToSettings()`` inside ``KeyboardHelper.setLayoutEnabled`` please add ``KeyboardHelper.saveToSettings()`` in ``app_install_manager``
  https://github.com/mozilla-b2g/gaia/blob/master/apps/system/js/app_install_manager.js#L298