Also adds a test contributed by jgilbert@mozilla.com.

Bug: angleproject:3375
Change-Id: Ibd52daa074bf53b2b213193ccf5a612705a89c67
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1565052Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>