Possible driver bug.

Bug: angleproject:3342
Change-Id: Ia171a7ac0d764859c4440b1fe2986aa931ff75c2
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1550799Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>