pull out schedule, finalize

This finishes up the main refactoring.
Still some follow-ups I want to try.

I got tired of typing usage.users(id) so I converted that to operator[],
which I think is clear for now.  If we add more methods that don't refer
to the users, we can undo?

Change-Id: I0ac563cfb1899f7a3f8b2cb6d50ca1646dd05071
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/281216
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed