This test makes sure that even if sampler / texture registers get
grouped together based on type in the HLSL backend of the shader
translator, the D3D renderer still has the right register index
information for each ESSL sampler.

BUG=angleproject:1261
TEST=angle_end2end_tests

Change-Id: Id09f96cfa903cd20c8e7229980fa363bb07b6045
Reviewed-on: https://chromium-review.googlesource.com/322200Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>