Prior to this commit, we also cleared out all of your checkboxes,
which is frustrating if you wanted to invite another person to the
exact same set of streams.
(imported from commit 389f27ec35dc9bf8c9058c5ffa867929ac90f674)
This is a tricky one because it's kind of hard to see locally, but
there's a bit of a delay between when you click "Invite" and when we
get back to you. So we give the button a "loading" state so you know
not to click again.
(imported from commit 9c3389a3d06def777427c846d6106f6d9b30cc8b)
Waseem Daher
Zev Benjamin