Comment 3 for bug 1237360

PauseDownload is currently no-op'd, but it should be easy to plumb this through to the download manager. We also need to plumb the u-d-m's paused signal through out through s-i's UpdatePaused signal. (Ideally, system-settings would talk directly to u-d-m, but IIRC didrocks wanted to keep things simple there and only talk to one service).

There's one tricky bit. Let's say the download is paused for longer than 10 minutes. If that happens, system-image-dbus will exit and lose its state (retaining state after a re-invocation is part of another bug, but we'll see if that gets fixed before saucy, since it's complicated).

We could suspend exiting the main loop when there's a download paused, but then we run the risk of keeping s-i-dbus alive effectively forever, since there's no other event that would cause it to exit. If we do that, I think we have to cancel any existing paused downloads.