GitLab

Refactored CloudPolicyValidator so that the base class doesn't expect
the policy_value() to be a protobuf. This is a preparation for the
support of extension policy for Active Directory managed devices, where
the policy_value() is a JSON blob.

Also removed the static Create methods. There's no reason to have them
as one can use the constructor directly. The rest is clang format.

BUG=chromium:735100
TEST=Trybots

Change-Id: Ic952c2cd00e945910f62d0ad08839282818d1d1e
Reviewed-on: https://chromium-review.googlesource.com/1002654Reviewed-by: Bartosz Fabianowski <bartfab@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Lutz Justen <ljusten@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550169}