WPT import https://crrev.com/c/1120145 introduced new failures in external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox:

List of new failures:
external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-column-row-gap-001.html [ Failure ]
external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-column-row-gap-002.html [ Failure ]

This import contains upstream changes from 7a6f5673ff5d146ca5c09c6a1b42b7706cfee328 to e639f5b4158852b16ffa28613730c2b0b63f5e83:
Allow specifying the mozilla tree via argument.: https://github.com/web-platform-tests/wpt/commit/e639f5b4158852b16ffa28613730c2b0b63f5e83 [affecting this directory]
Make sync-tests.sh work with git.: https://github.com/web-platform-tests/wpt/commit/8b61c282650bf72bce0147df320425343ea27f2f [affecting this directory]
Update the WebIDL file: https://github.com/web-platform-tests/wpt/commit/b23f2ac412b4b104f21ef7a724ead853e2fa0afa
Sync Mozilla tests as of https://hg.mozilla.org/mozilla-central/rev/6041c030780420b6205cf2d6640513606609884c: https://github.com/web-platform-tests/wpt/commit/dc302574be5e27db4ade270698c966a39a09e300 [affecting this directory]
Prepare ReplacementTokenizer for Python 3 (#11685): https://github.com/web-platform-tests/wpt/commit/a4b7841ea1345ffdcbd79e399f7ff1982fab5362
Update external/wpt/webrtc/RTCRtpParameters* tests.: https://github.com/web-platform-tests/wpt/commit/36fb033a4051e63a0ab4bd073fdaadf808953564
Worker: Add WPTs for module loading with blob, data, and file URLs: https://github.com/web-platform-tests/wpt/commit/a2c108ffd92458de51acc02a0f79221548c785ab