Related to:
https://chromium-review.googlesource.com/c/angle/angle/+/1520988
The program uniform buffers were dirtied for this edge case, but it
should have been the driver uniform buffers. This CL fixes this and adds
a tests case which catches this.

Bug: 945903
Change-Id: I6142771e200513ed0251fc97cec68d371d39ec1a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1565059
Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Shrek Shao <shrekshao@google.com>