Was a needed fix for a new varying test.

Bug: angleproject:3571
Bug: angleproject:5496
Change-Id: I49ae69967510b7a6330ea217a0e0e19e3bebe865
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2613198Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>