Hi Dave,
Yes, the update button is always visible and enabled. Clicking it, it updates the input fields of lat and long in the form. by getting the data from the browser. if it support geolocation APIs.
I was not aware of the MDL-42522 and all you development in github, although I was looking for any development in that area before I started my quick experiment. I guess I was using the wrong keywords while searching
MDL-42522 seems the best way to move forward with this. you have my vote!