iot/labs/Demo/Demo.Android/Controls/MyWebViewRenderer.cs

using Android.Annotation;
using Android.App;
using Android.Content;
using Android.Webkit;
using Demo.Droid.Controls;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(Xamarin.Forms.WebView), typeof(MyWebViewRenderer))]

namespace Demo.Droid.Controls
{
    public class MyWebViewRenderer : WebViewRenderer
    {
        private Activity mContext;

        public MyWebViewRenderer(Context context) : base(context)
        {
            this.mContext = context as Activity;
        }

        protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.WebView> e)
        {
            base.OnElementChanged(e);
            Control.SetWebChromeClient(new MyWebClient(mContext));
        }

        private class MyWebClient : WebChromeClient
        {
            private Activity mContext;

            public MyWebClient(Activity context)
            {
                this.mContext = context;
            }

            [TargetApi(Value = 21)]
            public override void OnPermissionRequest(PermissionRequest request)
            {
                mContext.RunOnUiThread(() =>
                {
                    request.Grant(request.GetResources());
                });
            }
        }
    }
}