Arrays of arrays have not been implemented yet, but these tests can
already be enabled. This is useful to make sure that we don't
accidentally enable arrays of arrays where they shouldn't be enabled
and that the initial implementation generates errors correctly and
doesn't crash on malformed inputs.

BUG=angleproject:2125
TEST=angle_unittests, angle_deqp_gles31_tests

Change-Id: I538e5ae1f0903c42e06cfce352124130f160649d
Reviewed-on: https://chromium-review.googlesource.com/620706Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>