Seperate vertex and fragment shader read/write with shader stage specific barriers Bug: angleproject:4467 Change-Id: Id18909b497b087e58d750023399943bc9d414edf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2102957 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
