Marked a failing test

Which is animation-direction-reverse.html.

TBR=dstockwell
BUG=268228

Review URL: https://codereview.chromium.org/22136002

git-svn-id: svn://svn.chromium.org/blink/trunk@155505 bbb929c8-8fbe-4397-9dbb-9b2b20218538