Closing Media prefs aborts media services restart

[humdinger]

This is hrev47114.

When you're restarting the media services from the Media preferences, the restarting is aborted when you close the Media prefs' window. An impatient user could close it prematurely.

Making the window showing the restarting progress modal would be a solution. But what if something goes wrong and the restarting gets stuck?
Maybe that progress window wouldn't be only modal, but also grow a quit button like a regular window. Then the user could abort the restarting if it gets stuck (which hasn't happened to me yet).

Another, maybe better solution, could be to decouple the restarting process and use notifications to inform the user of the progress.

[Barrett]

Fixed in hrev49465.