Take a snapshot of MapView.

use this method to take a picture of the MapView, returning a promise with the path argument of where the picture is stored

Examples:

<NativeViewHost>
    <MapView ux:Name="MapView" />
</NativeViewHost>
<JavaScript>
    MapView.snapshot()
        .then(function(path) {
            console.log(path);
        })
        .catch(function(err) { });
</JavaScript>