Gardening. Tweak web-animations-css/transitions expectations.

NOTRY=true
TBR=steveblock

Review URL: https://codereview.chromium.org/40103002

git-svn-id: svn://svn.chromium.org/blink/trunk@160445 bbb929c8-8fbe-4397-9dbb-9b2b20218538