Don't paint focus ring for anonymous block continuations

Now we push outline style to anonymous block continuations when the
containing inline style changes. As the inline paints the whole
focus ring, the anonymous block continuation should not paint focus
ring again.

Separated from https://codereview.chromium.org/481283003/ which has been
lgtmed.

BUG=393529
R=jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/496453004

git-svn-id: svn://svn.chromium.org/blink/trunk@180748 bbb929c8-8fbe-4397-9dbb-9b2b20218538