ESSL 3.00.4 section 4.6.1 says that using #pragma STDGL invariant(all)
in a fragment shader is an error, so make it an error. This spec
language is not found in ESSL 1.00, and it's been removed in ESSL 3.10.

BUG=angleproject:1276
TEST=angle_unittests

Change-Id: I2022f35475f867304b55dfb142f8568f6df28830
Reviewed-on: https://chromium-review.googlesource.com/321240
Tryjob-Request: Olli Etuaho <oetuaho@nvidia.com>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>