Reland "Add shelf owners to //ash/public/cpp/OWNERS"

This reverts commit 2e6f9474f58ddcd3f72f425d5af6a8dd77cab614.

Reason for revert: Relanding now that gerrit outage is over.

Original change's description:
> Revert "Add shelf owners to //ash/public/cpp/OWNERS"
> 
> This reverts commit e7591612da4c080af86c964d14b25c4061f5b51b.
> 
> Reason for revert: Due to Gerrit outage http://crbug.com/872722, we are reverting this CL. Please, re-land it after all clear is given. If you have questions, please ask on the bug. Sorry for the inconvenience.
> Original change's description:
> > Add shelf owners to //ash/public/cpp/OWNERS
> > 
> > Bug: none
> > Change-Id: Ib1fbca291732828c5b7feeaf853ed84a41970999
> > Reviewed-on: https://chromium-review.googlesource.com/1168646
> > Commit-Queue: James Cook <jamescook@chromium.org>
> > Reviewed-by: Michael Wasserman <msw@chromium.org>
> 
> TBR=jamescook@chromium.org,msw@chromium.org
> 
> Change-Id: I8b26db1fca95f8ff6b9b01c62911fb904570c50f
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: none
> Reviewed-on: https://chromium-review.googlesource.com/1169853
> Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>

TBR=jamescook@chromium.org,msw@chromium.org,tandrii@chromium.org

Change-Id: I9ea7352dd60261d0dd604854f8cc76686562f1d5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: none
Reviewed-on: https://chromium-review.googlesource.com/1171063
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582201}

ash/public/cpp/OWNERS

+per-file *shelf*=file://ash/shelf/OWNERS
+
 per-file *.mojom=set noparent
 per-file *.mojom=file://ipc/SECURITY_OWNERS