This could lead to a subtle bug:

Say we use a buffer as a storage buffer and write to it. We then must
issue a memory barrier before using it as a uniform buffer. However we
would set the SHADER_READ bit as a read mask on a storage buffer
access. This seems like it could lead to a missing barrier.

Bug: angleproject:4178
Change-Id: I486002739b7fb000ffacc0a1e996784b7875e7ba
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1943034
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>