We were assuming at least one variable, when some shaders could legitimately use zero. This was causing assertions in the dEQP shader.function tests. BUG=angle:855 Change-Id: I7e4aa52a1c6ba98d4a396f4c642816ff95115fd5 Reviewed-on: https://chromium-review.googlesource.com/240144Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
