Web Animations CSS: Adding manual test for animation-delay on compositor.

(Bug this test reveals is fixed in https://codereview.chromium.org/96093002/)

BUG=324378,324670

Review URL: https://codereview.chromium.org/96123002

git-svn-id: svn://svn.chromium.org/blink/trunk@162949 bbb929c8-8fbe-4397-9dbb-9b2b20218538