code: function useAmoPreviewUrls() {
    var prefSrv = prefs.preferences;
  
    for each (var preference in AMO_PREFERENCES) {
      var pref = prefSrv.getPref(preference.name, "");
      prefSrv.setPref(preference.name,
                      pref.replace(preference.old, preference.new));
    }
  }
docs: Updates all necessary preferences to the preview sub domain