Add clipboard permission type and context

This cl adds the basic Clipboard PermissionType and the
PermissionContext.

UX for this permission (which will be behind a feature flag) will
be added in a follow-up cl.

Bug: 677564
Change-Id: Ia5909c8f1feeedad5471db87630154071d7ba8ac
Reviewed-on: https://chromium-review.googlesource.com/759029
Commit-Queue: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517332}
20 files changed