Clean up change in preparation for changes that add more options.

Bug: angleproject:5478
Change-Id: Id35825b337dba153a5c28dfcc311b344ce257f78
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2599941
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>