Add a LayoutTest for animation iteration events when the duration is short

BUG=275263
R=dstockwell

Review URL: https://chromiumcodereview.appspot.com/22870010

git-svn-id: svn://svn.chromium.org/blink/trunk@156295 bbb929c8-8fbe-4397-9dbb-9b2b20218538