Before this patch, nsTableCellFrame never skips border and padding. If
it needs to be broken into multiple fragments, its children don't have a
correct available space to reflow. (A side effect of this is that
nsTableCellFrame renders correctly if it has
box-decoration-break:clone.)
table-nested-1308876-1-ref.html is modified to reflect the rendering
after applying this patch, which isn't necessarily correct (based on the
file's comment).
Differential Revision: https://phabricator.services.mozilla.com/D71096
