This now reports averaged time per frame instead of per "step".
Scores in general will be divided by 11. Results still reported
in nanoseconds.

Bug: angleproject:4920
Change-Id: I6f9dca75885cce358c3c7d1e871441969d8aa3d3
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2334095Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>