Convert fast/multicol/column-break-with-balancing (and related) to reftests.

 * Use standards mode.
 * Make test small enough to fit in content_shell.
 * Use fixed widths columns to simplify ref.

R=mstensho@opera.com
BUG=386567

Review URL: https://codereview.chromium.org/671433002

git-svn-id: svn://svn.chromium.org/blink/trunk@184184 bbb929c8-8fbe-4397-9dbb-9b2b20218538