StateManagerGL: Fix reserved indexed buffer count. 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/754721 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>