This test was flaky, the failure was missed on the CQ.

Bug: angleproject:2484
Change-Id: Ic3c32bcd385620683e9a01acf37d62bbf3ca8797
Reviewed-on: https://chromium-review.googlesource.com/1014733Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>