Add tools/perf essential Python files.
While waiting for the full mirror we can simply duplicate the
minimal necessary files for angle_perftests to run.
Test: mb.py zip
Bug: angleproject:5114
Change-Id: I1847909cb78b32efed26a284fdfcd40ed31d7b4b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2862922
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
