We were reserving the count of shader resource limits instead of API-
side binding limits. This fixes a broken dEQP test that was only
showing up in some device configs. Also add an ASSERT.

See:
dEQP-GLES31.functional.layout_binding.ubo.fragment_binding_max_array

BUG=angleproject:1920

Change-Id: I993ebc7993cc3cc78e90f74e097c0bbab9d03909
Reviewed-on: https://chromium-review.googlesource.com/754721Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>