GitLab

Makes one reusable macro for disabling the tests on Windows and Mac,
instead of having to define a new one each time.

Bug: 894854
Change-Id: Ic01ec8e6bea07b76a3e0dceec62084b5c6321256
Reviewed-on: https://chromium-review.googlesource.com/c/1306398Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603646}