This support was missing and caused dEQP crashes.

Bug: angleproject:3627
Change-Id: Idc06cc92df676061f8a08d0f32a1b3e7f03a66f4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1691102
Commit-Queue: Ian Elliott <ianelliott@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>