Mark svg/carto.net/window.svg as flaky on Mac

BUG=326881
TBR=pdr@chromium.org

Review URL: https://codereview.chromium.org/107513006

git-svn-id: svn://svn.chromium.org/blink/trunk@163393 bbb929c8-8fbe-4397-9dbb-9b2b20218538