WPT import https://crrev.com/c/1034213 introduced new failures in external/wpt/infrastructure:

List of new failures:
external/wpt/infrastructure/browsers/firefox/prefs.html new failing tests: https://crrev.com/c/1034213/4/third_party/WebKit/LayoutTests/external/wpt/infrastructure/browsers/firefox/prefs-expected.txt

This import contains upstream changes from b51b155ffce7a030397dc173e20628ae2742e030 to cc364d6f98b111e488aa1d88064af21566ec4184:
Merge pull request #10539 from tabatkins/css-syntax-whitespace: https://github.com/w3c/web-platform-tests/commit/cc364d6f98b111e488aa1d88064af21566ec4184
Use link, not meta.: https://github.com/w3c/web-platform-tests/commit/c9da3e34db3e6eab364e844c1495972bfc044668
Add tests for floats next to new formatting contexts.: https://github.com/w3c/web-platform-tests/commit/ea89515a92d0580fc85e9cff8aa6895c9aa509f5
Rename a WPT: https://github.com/w3c/web-platform-tests/commit/da2fb690481adb7fda393474459c066568b96029
Make KeyframeEffectReadOnly::setKeyframes take effect immediately: https://github.com/w3c/web-platform-tests/commit/e7d3e5206b87ece7e9c80b46a21740d508f924da
Use less-verbose mach logs for stdout.: https://github.com/w3c/web-platform-tests/commit/ee911cd691204506a63a651e2411db422a876be2
Ensure we have enough commits that a manifest can be downloaded: https://github.com/w3c/web-platform-tests/commit/f259d821cfb915164a71759938a69c58e391f2c6
Explicitly set Firefox to use the fast reftest runner.: https://github.com/w3c/web-platform-tests/commit/1e51e1722a294830c85866462757d6924de7bac4
Set taskcluster log level to INFO: https://github.com/w3c/web-platform-tests/commit/83e53587e7400d7119681ec0810e562d401fcfe6
Bump the versions of some moz* dependencies: https://github.com/w3c/web-platform-tests/commit/500811b1ae3a2fd90212258125cb979dcb0a0768
P3 Fix tests to expect ServiceWorkerRegistration.update() to resolve with a registration.: https://github.com/w3c/web-platform-tests/commit/e7523c1fd6ba45a326535caeefcf06a001bf2dca
Add a infrastructure test to ensure that we can set Firefox prefs.: https://github.com/w3c/web-platform-tests/commit/a12d3faef43491233345c225377546cbb09f4799 [affecting this directory]
typo: https://github.com/w3c/web-platform-tests/commit/a9dc3a39c87f80463bee8d6fab6de3e978ef8c41
Switch to spaces, ugh.: https://github.com/w3c/web-platform-tests/commit/176f2f33a0360938300fc44ee4269458306d3735
Add rel=help, correct author: https://github.com/w3c/web-platform-tests/commit/326f7c676de189c2286e0d39ddf87c179ccdd3e5
Correct folder.: https://github.com/w3c/web-platform-tests/commit/32dbe741ed8af22ed380960178307fb739819fbc
Test for https://github.com/w3c/csswg-drafts/pull/1986: https://github.com/w3c/web-platform-tests/commit/5198b66ade80a17b3fb850d84aecf21dd40aea53