Gardening: virtual/deferred and virtual/gpu failures on Mac since r264636

Mark a couple of virtual/deferred and virtual/gpu image tests as
failing on Mac.

TBR=danakj@chromium.org
BUG=364946

Review URL: https://codereview.chromium.org/242643005

git-svn-id: svn://svn.chromium.org/blink/trunk@171967 bbb929c8-8fbe-4397-9dbb-9b2b20218538