void HandleBrowsingCompleted(object sender, EventArgs e)
        {
            if (!webViewVisible)
            {
                return;
            }

            if (authenticatingView == null)
            {
                authenticatingView = new UIView(View.Bounds)
                {
                    AutoresizingMask = UIViewAutoresizing.FlexibleWidth | UIViewAutoresizing.FlexibleHeight,
                    BackgroundColor  = UIColor.FromRGB(0x33, 0x33, 0x33),
                };
                progress = new ProgressLabel("Authenticating...");
                var f = progress.Frame;
                var b = authenticatingView.Bounds;
                f.X            = (b.Width - f.Width) / 2;
                f.Y            = (b.Height - f.Height) / 2;
                progress.Frame = f;
                authenticatingView.Add(progress);
            }
            else
            {
                authenticatingView.Frame = View.Bounds;
            }

            webViewVisible = false;

            progress.StartAnimating();

            UIView.Transition(
                fromView: webView,
                toView: authenticatingView,
                duration: TransitionTime,
                options: UIViewAnimationOptions.TransitionCrossDissolve,
                completion: null);
        }
		void HandleBrowsingCompleted (object sender, EventArgs e)
		{
			if (!webViewVisible) return;

			if (authenticatingView == null) {
				authenticatingView = new UIView (View.Bounds) {
					AutoresizingMask = UIViewAutoresizing.FlexibleWidth | UIViewAutoresizing.FlexibleHeight,
					BackgroundColor = UIColor.FromRGB (0x33, 0x33, 0x33),
				};
				progress = new ProgressLabel ("Authenticating...");
				var f = progress.Frame;
				var b = authenticatingView.Bounds;
				f.X = (b.Width - f.Width) / 2;
				f.Y = (b.Height - f.Height) / 2;
				progress.Frame = f;
				authenticatingView.Add (progress);
			}
			else {
				authenticatingView.Frame = View.Bounds;
			}

			webViewVisible = false;

			progress.StartAnimating ();

			UIView.Transition (
				fromView: webView,
				toView: authenticatingView,
				duration: TransitionTime,
				options: UIViewAnimationOptions.TransitionCrossDissolve,
				completion: null);
		}