Rewrite fast/multicol/positive-leading-expected.html as a reftest.

R=andersr@opera.com
BUG=386567

Review URL: https://codereview.chromium.org/885143003

git-svn-id: svn://svn.chromium.org/blink/trunk@189786 bbb929c8-8fbe-4397-9dbb-9b2b20218538
8 files changed