Reflow table cell if collapsed borders have changed.
A potentially better approach could be to call FrameNeedsReflow from
nsBCTableCellFrame::SetBorderWidth... But it seems that might
over-invalidate quite a lot when recalculating borders, since it seems
we reset the relevant ones and then accumulate directly on the frame.
If that seems like a better approach, happy to give that a try. This
should be less risky for performance changes in general tho.
Differential Revision: https://phabricator.services.mozilla.com/D216409
bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1907289
gecko-commit: a3485259ae0ce7c192e2b9567e5b9fc4cfbf8aad
gecko-reviewers: dshin