Fix buttons after the latest refactor.

Just some styling and import boogs, but they meant buttons
didn't render at all.

NOTRY=true
TBR=leviw@chromium.org

Review URL: https://codereview.chromium.org/564023002

git-svn-id: svn://svn.chromium.org/blink/trunk@181869 bbb929c8-8fbe-4397-9dbb-9b2b20218538