closeAndDisableWelcomeScreen_() {
    var checkbox = this.getElement().querySelector('input');
    e2e.ext.utils.action.getPreferences(
        function(preferences) {
          preferences.setWelcomePageEnabled(checkbox.checked);
          window.close();
        },
        function() {
          window.close();
        });
  }
Closes and disables the welcome page.
@private