Add state change test for uniform buffer validation. Bug: angleproject:2747 Change-Id: Ia808e26a48ecf432cc29ebd8514f265ff3e15ce8 Reviewed-on: https://chromium-review.googlesource.com/1169825 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>