Use invalidation set for :empty pseudo changes.

Schedule an invalidation set for :empty on an element when the pseudo state
changes instead of a SubtreeStyleChange.

R=chrishtr@chromium.org,esprehn@chromium.org
BUG=412999

Review URL: https://codereview.chromium.org/565493002

git-svn-id: svn://svn.chromium.org/blink/trunk@181805 bbb929c8-8fbe-4397-9dbb-9b2b20218538