This was preventing testing with the viewport flip disabled.

Bug: angleproject:5596
Change-Id: I5cc39eb2e1b431625f2f1498ab73828961af42ee
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2664249
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>