Add policy handler for cookie controls

When third party cookies are managed by enterprise policy, the
cookie controls preference needs to be forced to be disabled.

Bug: 967668
Change-Id: I68a78d083157c63fa9cfe088b097c73f9f3f1ea2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1658156
Commit-Queue: Christian Dullweber <dullweber@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672050}