FormsApplicationDelegate OpenURL not being called

Hey
I am trying to register a custom file type to associate with the App, and open the email attachment with the App. I can open the app when select the attachment, but the OpenURL event handler is not being fired.
I created a sample Xamarin forms solution(Shared code) with latest stable version of Xamarin.Forms 1.3.1.6296, and add the following code to AppDelegate.cs

public override bool OpenUrl (UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
{
Console.WriteLine ("Invoked with OpenUrl: {0}", url.AbsoluteString);
return true;
}
I also added the OnActivated, it is never fired as well

    public override void OnActivated (UIApplication application) { 
        Console.WriteLine ("Activated");

    } 

is it related with the fact that I am using Xamarin forms?
Any advice/help will be appreciated.

Sunny