Re-enable blink_perf.web_animations

Web Animation perf tests no longer crash.
Fix occurred in: https://codereview.chromium.org/73643003/

BUG=320042

Review URL: https://codereview.chromium.org/77733002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236438 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236438