Rebaseline visibility-image-layers.html on Mac

BUG=407538
TBR=ccameron@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/502253003

git-svn-id: svn://svn.chromium.org/blink/trunk@180903 bbb929c8-8fbe-4397-9dbb-9b2b20218538