Any solution for OAuth Google without webviews

I'm developping an app in which I'd like the user to log with fb or google account. So far I've been using Xamarin Auth which provides a OAuth authentification with webviews.

As I want to realease the app on markets, I checked the future deprecation of this component. Google made an annoucement saying that they will block any OAuth in webviews from April 20th 2017 ...

Have you find a solution to Xamarin Auth for google sign in ?

I've seen a component for FireBase published by xamarin 25 days ago ... but I wonder if it will work for forms as it is a xamarin android component ... And I'd like to keep the logic that "forms is crossplatform" and I do not want to use a plugin for each project.

I've been seeking the web but no solutions...

I'm glad if someone's found something or a workaround without components if there are none ..