Adjust breaks-3-columns test to pass on Windows

Adjust the width of each column for the fast/multicol/newmulticol/
breaks-3-columns-3.html test so to allow the slightly wider text
on Windows with DirectWrite.

TBR=dglazkov@chromium.org
BUG=378610

Review URL: https://codereview.chromium.org/330693002

git-svn-id: svn://svn.chromium.org/blink/trunk@176054 bbb929c8-8fbe-4397-9dbb-9b2b20218538