This is a reland of a84eaf51

Original change's description:
> git-cache: Start collecting metrics.
>
> Change-Id: I36f4b37a78ad23d615e3f49f158e8de785d5214a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2875855
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

Change-Id: I80091d78deb0b1aaba280572a1384848990d9d93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2877262Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>