GitLab

- Enable CHECK against registration of new keep-alives during shutdown.
- Promote some DLOG() checks to DCHECKs to make issues more visible.

Bug: 720078
Change-Id: I11e24a8de0ec5ab9e0a71f776d4b7149bb847ad2
Reviewed-on: https://chromium-review.googlesource.com/1013394Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551033}