WPT import https://crrev.com/c/1265027 introduced new failures in external/wpt/css/css-multicol:

List of new failures:
external/wpt/css/css-multicol/multicol-span-all-margin-bottom-001.xht [ Failure ]

This import contains upstream changes from ed1e1878f364d9c7aa488fa4e7397bae937fee02 to 1fa98500b503b310250ba846523f90f7fd5c6b39:
Fix wpt test multicol-span-all-margin-bottom-001-ref.xht.: https://github.com/web-platform-tests/wpt/commit/1fa98500b503b310250ba846523f90f7fd5c6b39 [affecting this directory]
[Background Fetch] Reject calls to get with invalid IDs.: https://github.com/web-platform-tests/wpt/commit/8e9df70029090145da7c2d2e78af4d65dd9caa8b
Resubmit cr/1261477: https://github.com/web-platform-tests/wpt/commit/786e201985b7c46ef59185c2c519f9081374fb2a