BUG=angleproject:2280
TEST=dEQP-GLES31.functional.compute.basic.image_barrier_single
     dEQP-GLES31.functional.compute.basic.image_barrier_multiple
     dEQP-GLES31.functional.compute.basic.ssbo_cmd_barrier_single
     dEQP-GLES31.functional.compute.basic.ssbo_cmd_barrier_multiple
     dEQP-GLES31.functional.synchronization.*

Change-Id: If14debab21247dc4b446e86d1642fbc9376b6dd7
Reviewed-on: https://chromium-review.googlesource.com/798803
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>