Disable resize tests for pinch virtual viewport on Mac OSX.

They are flaky, work locally but fail on buildbot.
Need to investigate the failure.

BUG=418845

Review URL: https://codereview.chromium.org/613753004

git-svn-id: svn://svn.chromium.org/blink/trunk@182883 bbb929c8-8fbe-4397-9dbb-9b2b20218538