The uniform name by default has the array subscript [0] appended. In
the shader code it uses no subscript. Fix this by parsing out the
subscript in the glslang wrapper subsitution step.

This is a preliminary fix. More work on descriptor set layouts and
pipeline layouts will be necessary to support sampler arrays.

Bug: angleproject:2462
Change-Id: I57d6304f33822d588c7cb192607380c2f3ba20f5
Reviewed-on: https://chromium-review.googlesource.com/1089808
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Frank Henigman <fjhenigman@chromium.org>