WPT import https://crrev.com/c/1192593 introduced new failures in external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox:

List of new failures:
[ Mac10.10 Mac10.12 ] external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-intrinsic-ratio-003v.html [ Failure ]

This import contains upstream changes from 2c9aebf2096ec338064b494f3cdf6a3ffc9ac802 to 3d172bc612e03a896b5611d9e9652f860995feef:
Fetch/XHR: response header value containing 0x00: https://github.com/web-platform-tests/wpt/commit/3d172bc612e03a896b5611d9e9652f860995feef