Per-stage uniform buffers are marked with the specific stage.  Program
uniform buffers and images are specified to be used in all graphics
stages.  Descriptors used in internal shaders are marked for use in
either compute or fragment stages.

Bug: angleproject:3220
Change-Id: Ifcac36a1224f0392ba5fba50660514e498256401
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1595439
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tobin Ehlis <tobine@google.com>