SystemSoundTest.FromFile was requesting to be called back when the sound
completed playback. This causes problems when the sound is disposed after it
has started playing, because in that case disposing it won't prevent the
callback from being called, but instead random InvalidCastExceptions / crashes
would occur.
https://bugzilla.xamarin.com/show_bug.cgi?id=52903
* SystemSound.PlaySystemSound doesn't work in the simulator.
https://stackoverflow.com/a/24973240/183422