These transitions were incorrectly handled by an execution barrier
alone, but that's not per spec.  Write-after-write hazards always need a
memory barrier.

Bug: angleproject:3347
Bug: angleproject:3554
Change-Id: Id2d2579888e0b59e589fcdd52416363f2cf5cf97
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1943546Reviewed-by: Tobin Ehlis <tobine@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>