c0c34eb571
This makes alert take the same area as the status panel, partially backing out the regressing bug. .browserStack is also relatively-positioned, so this works too. I think I didn't realize this while writing bug 1791972 because the rule was in a UA sheet (all <stack>s are relatively positioned, apparently). This restores the behavior when devtools is toggled vertically. On responsive mode this still covers the top toolbar, but that was the pre-existing behavior. Could be fixed in a follow-up with some z-index tweaking... Differential Revision: https://phabricator.services.mozilla.com/D162739