DNR: Have RulesetSource constructor take in the ID and priority.

This helps get rid of a couple of "for_testing" methods.

BUG=930961

Change-Id: I1b3aa05a1e755a8009aa7888af8ddccf5339ae4a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1533000
Auto-Submit: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643102}
6 files changed