This switch can be cached in a very fast packed map. The map contents
only change if different extensions are exposed. This reduces the
number of instructions we hit in ValidateBindTexture.
Bug: angleproject:2763
Change-Id: I6ba8a4124d85e4c193d0dee3e03e50713d51b1f4
Reviewed-on: https://chromium-review.googlesource.com/c/1262739
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@google.com>
