Code review comment for lp:~mterry/indicator-sound/greeter-volume

As discussed on IRC, I don't want to check username because the greeter user is a sysadmin-configurable option. But I can check an environment variable that LightDM sets that can tell us if we are in greeter. That's done.

I made the greeter interface an object.

But on using accounts service lib or a vala interface object for AccountsService, I'm going to give soft pushback. The lib isn't async nor can vala interface objects expose async property getter/setters. And since this is in UI code (like, this code is run when the user moves the volume control), I don't think making sync calls is appropriate.