Reland "git-cache: Start collecting metrics."
Reland "git-cache: Start collecting metrics."

This is a reland of a84eaf515f9dd4f199425e0cfc46f3e1b2b0984a

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 <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>

Change-Id: I80091d78deb0b1aaba280572a1384848990d9d93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2877262
Reviewed-by: Anthony Polito <05bb588aa9020353543fee7ac4e6e0a3d0d6f6ed@google.com>
Commit-Queue: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools