Add a draw call perf test for changing a single uniform. Bug: angleproject:6776 Change-Id: I0621c813a654b3378b48d03219620627605b24a5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3638984 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>