When a component registers after having already registered once, there
are two sources of truth for the version ID: one implicit in the
connection to Megaphone, and one coming from the component call to
addListener. Try to handle this more thoroughly.
MozReview-Commit-ID: EsYgO0mzQ9w
--HG--
extra : rebase_source : c4823e44733f218da842aabf5c0961500a461c82