Replace fast/multicol/float-paginate-complex with float-big-line.

The test float-paginate-complex adds nothing over the other float-* tests,
except the case with a big line box. That case has been split out into
a new reftest: float-big-line.

R=mstensho@opera.com
BUG=386567

Review URL: https://codereview.chromium.org/699593003

git-svn-id: svn://svn.chromium.org/blink/trunk@184876 bbb929c8-8fbe-4397-9dbb-9b2b20218538