Without this, in my testing with the previous patch, the scroll alignment on
the initial load of the settings page is incorrect, with the top of the
section being cut off. As this is the situation we care about (first load after
a browser update), fixing it seemed important.
I spent some time trying to work out why layout is changing - presumably
items above the "Browser Layout" section are either appearing or disappearing
in a way that races with the scroll. I could never reproduce on any loads other
than the first one. But then I realized the code here was overly complex and
that it would probably be nicer for items to appear in the middle of the view
rather than the top anyway. Yes, this means that sometimes the relevant header
is _still_ not _exactly_ in the middle, but that seems much less important.
Differential Revision: https://phabricator.services.mozilla.com/D241628
b3fbe6b83e
