Can be useful for perf testing.

Bug: angleproject:4729
Change-Id: I26c5fd53a34f4ed21d565e020b7c2058ff7ee6db
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2241621Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>