public static function userCanBitfield( $bitfield, $field, User $user, Title $title = null ) {
	// ...

	// XXX: How can we avoid global scope here?
	//      Perhaps the audience check should be done in a callback.
	$permissionManager = MediaWikiServices::getInstance()->getPermissionManager();

protected function userCan( $field, User $user ) {
	// TODO: use callback for permission checks, so we don't need to know a Title object!
	return self::userCanBitfield( $this->getVisibility(), $field, $user, $this->mTitle );
}