BUG=angleproject:1442
TEST=angle_unittests, angle_end2end_tests
     dEQP-GLES31.functional.compute.shared_var.atomic*
     dEQP-GLES31.functional.compute.basic.shared_atomic_op*
     dEQP-GLES31.functional.ssbo.atomic.*

Change-Id: I82b54fde3a852d3bd917b1e19680baa1c28fce4d
Reviewed-on: https://chromium-review.googlesource.com/765061
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>