GitLab

This patch implements RevokePermission() method in the mojo
PermissionService. This method will probably be for internal
use only for now. The semantics of the method is that it
will reset the permission to its default value in chrome if
the permission is currently granted.

BUG=430238

Review URL: https://codereview.chromium.org/819463002

Cr-Commit-Position: refs/heads/master@{#314163}