Forking off from  issue 594309 , the following tests are showing up on the flakiness dashboard:

Occasional failures:
external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-baseline-align-self-baseline-vert-001.html

Consistent failures in Linux and Win:
external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-baseline-multi-item-vert-001.html

Marked as LEAK in TestExpectations but green on flakiness dashboard:
external/wpt/css/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-whitespace-handling-002.xhtml