Fixes:
dEQP-GLES3.functional.shaders.texture_functions.textureproj.sampler2dshadow_fragment
dEQP-GLES3.functional.shaders.texture_functions.textureproj.sampler2dshadow_bias_fragment
dEQP-GLES3.functional.shaders.texture_functions.textureprojoffset.sampler2dshadow_fragment
dEQP-GLES3.functional.shaders.texture_functions.textureprojoffset.sampler2dshadow_bias_fragment
and some of:
dEQP-GLES3.functional.shaders.texture_functions.texture*.sampler2dshadow_vertex

BUG=angle:925

Change-Id: I080e379ded95469f0486ae9c8bb1756842118a2d
Reviewed-on: https://chromium-review.googlesource.com/251530Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Nicolas Capens <capn@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>