Network Service: CookieManager observer API refactoring.

This CL aligns CookieManager's interface for listening to cookie changes
(observer pattern) with the proposed addition to
RestrictedCookieManager, which will be used by the Async Cookies API.

Bug: 729800
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I0464b0d1d0388279e549d19c5dbeea2d0342cc60
Reviewed-on: https://chromium-review.googlesource.com/913151
Reviewed-by: Randy Smith <rdsmith@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536944}
6 files changed