Rebaseline Mac failures after r173781

These are all platform-specific scrollbar image differences.

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

Review URL: https://codereview.chromium.org/274203003

git-svn-id: svn://svn.chromium.org/blink/trunk@173790 bbb929c8-8fbe-4397-9dbb-9b2b20218538