In gms.location.FusedLocationProviderApi, the way to check if location settings are enabled is to call checkLocationSettings. That's great for polling, but it's possible for the user to turn location on/off using the new Quick Settings menu (swipe down from top), which does not necessarily trigger onResume in the top activity (if location is turned on, there's a dialog, but if it's turned off, there isn't one).
What's the right way to get notified when a Quick Setting toggles Location?