Fix repaint on :hover for empty elements with a border.

If the color changes on :hover, then the border of the element may need to
be repainted. Currently, we only repaint if an immediate child has a
border, but not if the element itself has a border. This causes a missing
repaint in some cases for bordered elements with whitespace-only contents.

Fixed by repainting when the element itself has a border.

BUG=275044
TEST=automated

Review URL: https://codereview.chromium.org/140673006

git-svn-id: svn://svn.chromium.org/blink/trunk@166654 bbb929c8-8fbe-4397-9dbb-9b2b20218538