This class is no longer used.

Bug: angleproject:4029
Change-Id: I2758b286ae10856a5dff3decbb1cf9c58b44e354
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2260936Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>