This value is HLSL-only and we can use the new query API to hide it
from GLSL programs.

BUG=angle:466

Change-Id: I75dc2fbbf1b29b1f6d561568174a15dea1f5b130
Reviewed-on: https://chromium-review.googlesource.com/207250Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>