public class App : Application
    {
        public App()
        {
            // The root page of your application
            var content = new ContentPage
            {
                Title = "App1",
                Content = new ScrollView
                {

                    Content = new WebView
                    {
                        Source = "https://www.stackoverflow.com"
                    }
                    //If I use entry rather than webview, it works.
                    //Content = new Entry
                    //{
                    //    VerticalOptions = LayoutOptions.End
                    //}
                }
            };

            MainPage = new NavigationPage(content);
        }
    }

.........
    [Activity(Label = "App1", Icon = "@drawable/icon", Theme = "@style/MainTheme", MainLauncher = true
        , ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation
        , WindowSoftInputMode = SoftInput.AdjustResize
        )]
    public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {
        protected override void OnCreate(Bundle bundle)
        {
            TabLayoutResource = Resource.Layout.Tabbar;
            ToolbarResource = Resource.Layout.Toolbar;

            base.OnCreate(bundle);

            global::Xamarin.Forms.Forms.Init(this, bundle);
            LoadApplication(new App());
        }
    }