This uses the protobuf histogram functionality to build up a histogram
set. The test suites then output the histograms to JSON. This is only
implemented for angle_perftests.

Bug: angleproject:5161
Change-Id: Ia5a7868e8d8dcf4f13d83115ae622828c63ef0d9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2482295Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>