There's quite a few changes in here. At a high level, all we're trying to do
is to replace the old update popup with a less intrusive and more modern
doorhanger (set of doorhangers) for various update failure conditions.
MozReview-Commit-ID: 24sESMTosNX
--HG--
extra : rebase_source : ee0c1e00fe3f99e16388f0de17274ff97a3b9fcf
