... while verifying that compressed textures work.

Bug: angleproject:3197
Change-Id: Icd25b761594fd51bbb6bc6963618caae8e4deec9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1680067Reviewed-by: Ian Elliott <ianelliott@google.com>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>