Add a test for :hover on display: block elements as per crbug.com/253472

I verified that this would have caught the regression by testing
with and w/o the revert.

BUG=253472
TBR=leviw

Review URL: https://codereview.chromium.org/19667002

git-svn-id: svn://svn.chromium.org/blink/trunk@154418 bbb929c8-8fbe-4397-9dbb-9b2b20218538