This would needlessly create many redundant sampler objects.

Bug: angleproject:4517
Change-Id: Ib8ef28b9bcbbeec804c493fbe677cbee7d9a750d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2159296
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>