Disabled sliming paint related test failures on Mac 10.6 introduced by blink@185263

BUG=432822
TBR=trchen@chromium.org, senorblanco@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/723953002

git-svn-id: svn://svn.chromium.org/blink/trunk@185275 bbb929c8-8fbe-4397-9dbb-9b2b20218538