Fix up Mac layout test baselines after r174041

These are all scrollbar image differences.

NOTRY=true
TBR=dpranke@chromium.org
BUG=361729

Review URL: https://codereview.chromium.org/282023002

git-svn-id: svn://svn.chromium.org/blink/trunk@174044 bbb929c8-8fbe-4397-9dbb-9b2b20218538