If bookmarks toolbar is empty (except for the flex space) the
empty-toolbar indicator element is visible, which causes the flex-space
to be be center-aligned - this is simply fixed with order: -1
In addition, when letterboxing is enabled and window is somewhat narrow,
the Done ::before pseudo can cause the statuspanel to be wider that the
<browser> element, which causes the <browser> to move when links are
being hovered. So lets just make the Done label absolute.
Flexbox model will replace old xul box as the default display model so
this patch adds support for that in a whole bunch of styles.
A lot of style rules are marked as "Fx < 112 compatibility" rules and
those can be removed when 112 hits release.
browser-bottombox doesn't exist anymore so create space using
body::after instead. This patch additionally fixes various alignment
issues with elements in the statusbar.
Normally web-content hides the real statusbar but with RFP letterboxing
that might not happen. So lets inherit the background-color from
tabbrowser-tabpanels to make sure it's covered properly.
