Currently this handles uniform block bindings. Cleans up some logic in D3D.

Bug: angleproject:2747
Change-Id: I8c2989738d50a77d6f6d90a9ff11dceab6d3129c
Reviewed-on: https://chromium-review.googlesource.com/1172085Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>