Convert fast/multicol/column-rules to reftest.

Notable changes:

 * Used fixed multicol container width.
 * Specify column-gap.
 * Specify line-height.

R=mstensho@opera.com
BUG=386567

Review URL: https://codereview.chromium.org/688323002

git-svn-id: svn://svn.chromium.org/blink/trunk@184721 bbb929c8-8fbe-4397-9dbb-9b2b20218538