This test has been intermittently failing for at least a week.

Link to latest failure:
https://uberchromegw.corp.google.com/i/chromium.webkit/builders/WebKit%20Win7/builds/50040

Failure snippet:
12:43:38.234 4448 [16593/47860] external/csswg-test/css-flexbox-1/flexbox_flex-natural-mixed-basis-auto.html failed unexpectedly (reference mismatch)
12:43:38.227 260 worker/7 external/csswg-test/css-flexbox-1/flexbox_flex-natural-mixed-basis-auto.html failed:
12:43:38.227 260 worker/7  reference mismatch

Should mark this as flaky in Webkit TestExpectations file and re-enable when it is more reliable.