estoy siguiendohttps://firebase.google.com/docs/auth/ y quiero usar FirebaseUI (https://github.com/firebase/FirebaseUI-iOS/tree/master/FirebaseUI) para la autenticación.

La interfaz de usuario se muestra correctamente y puedo hacer clic en "iniciar sesión con google" y luego completar el flujo de inicio de sesión web. La aplicación se vuelve a abrir con la URL de autenticación, pero la función authUI nunca se activa. Que pasa

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    // Override point for customization after application launch.
    FIRApp.configure()

    let authUI = FIRAuthUI.authUI()!;
    NSLog("setting up delegate");
    authUI.delegate = self;

    let googleAuthUI = FIRGoogleAuthUI.init(clientID:FIRApp.defaultApp()!.options.clientID);

    authUI.signInProviders = [googleAuthUI!];


    mSplitViewController = self.window!.rootViewController as! UISplitViewController


    self.window!.rootViewController = authUI,.authViewController();

    return true
}

    func authUI(authUI: FIRAuthUI, didSignInWithUser user: FIRUser?, error:NSError?) {
    // Implement this method to handle signed in user or error if any.
    NSLog("logged in");

    self.window!.rootViewController = mSplitViewController
    let navigationController = mSplitViewController!.viewControllers[mSplitViewController!.viewControllers.count-1] as! UINavigationController

    navigationController.topViewController!.navigationItem.leftBarButtonItem = mSplitViewController!.displayModeButtonItem()
    mSplitViewController!.delegate = self

    let masterNavigationController = mSplitViewController!
        .viewControllers[0] as! UINavigationController
    let controller = masterNavigationController.topViewController as! MasterViewController
    controller.managedObjectContext = self.managedObjectContext
}


func application(application: UIApplication,
    openURL url: NSURL, options: [String: AnyObject]) -> Bool {
        NSLog("opened with url \(url)");
        FIRAuthUI.authUI()!.delegate = self;
        return FIRAuthUI.authUI()!.handleOpenURL(url, sourceApplication:options[UIApplicationOpenURLOptionsSourceApplicationKey] as! String);
}