[jsapi4] cannot show full extent of a GraphicsLayer.

[terenceng2010]

             //this does not work, see https://community.esri.com/thread/192089-how-do-i-find-the-extent-of-an-array-of-graphics-in-js-api-4x
             //this.mapView.extent = layer.fullExtent;
             //use mapView.goTo instead
             this.mapView.goTo(layer.graphics);