Refactor uniform matrix entry points. This should also slightly speed up some of the validation. BUG=angleproject:747 BUG=angleproject:1390 Change-Id: I60735e2773788aef3f535bf7d3d8cd27bc4df5b1 Reviewed-on: https://chromium-review.googlesource.com/637123 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>