ES31: support ssbo as an argument of aggregate type BUG: angleproject:1951 Change-Id: Icaab8ffd0ee88cca22ba79a9f0d4e02c9134a169 Reviewed-on: https://chromium-review.googlesource.com/c/1349071 Commit-Queue: Jiajia Qin <jiajia.qin@intel.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>