This more easily allows us to compute the format alignment for use with
the vertex input stage.

Bug: angleproject:2797
Change-Id: If15281ce18fbed743b6a0c843cece4626bc4ce72
Reviewed-on: https://chromium-review.googlesource.com/1245841Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Jie A Chen <jie.a.chen@intel.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>