Correctly skip multiple failure annotations.
Sync Mozilla tests as of https://hg.mozilla.org/mozilla-central/rev/941bee559cd7 .

--HG--
rename : contributors/mozilla/submitted/mozilla-central-reftests/flexbox/flexbox-align-self-baseline-horiz-1.xhtml => contributors/mozilla/submitted/mozilla-central-reftests/flexbox/flexbox-align-self-baseline-horiz-1a.xhtml
Sync Mozilla tests as of https://hg.mozilla.org/mozilla-central/rev/822d8b27f427 .