After enabling column-span, ColumnSet becomes an anonymous child under
ColumnSetWrapperFrame. It doesn't need to handle border and padding,
containment, and non-auto block-size. ColumnSet's final block-size is
simply the union of ::-moz-column-content frames' rects.
However, we should extend ColumnSet's block-size to consume the
available block-size if the ColumnSetWrapper's block-size is constrained
so that the column rules are drawn to the block-end edge of the multicol
container.
Differential Revision: https://phabricator.services.mozilla.com/D39060
--HG--
rename : testing/web-platform/meta/css/css-multicol/multicol-breaking-000.html.ini => testing/web-platform/meta/css/css-multicol/multicol-rule-nested-balancing-001.html.ini
rename : testing/web-platform/meta/css/css-multicol/multicol-breaking-000.html.ini => testing/web-platform/meta/css/css-multicol/multicol-rule-nested-balancing-002.html.ini
rename : testing/web-platform/meta/css/css-multicol/multicol-breaking-000.html.ini => testing/web-platform/meta/css/css-multicol/multicol-span-all-rule-001.html.ini
extra : moz-landing-system : lando
