transitions/cancel-and-start-new.html is also flaky on XP

BUG=None
TBR=keishi, dpranke

Review URL: https://codereview.chromium.org/545983002

git-svn-id: svn://svn.chromium.org/blink/trunk@181474 bbb929c8-8fbe-4397-9dbb-9b2b20218538