Introduce a device setting controlling allowed connection types for AU.

Currently, the updater just updates on WiFi and Ethernet and we'd like
to be more flexible in what connection types we allow updates on. This
only introduces the setting (which also allows policy control). A
follow-up change on the Chrome OS side is needed to wire up
update_engine.

BUG=chromium-os:31099
TEST=Compiles and passes tests, no user visible changes (yet).

Review URL: https://chromiumcodereview.appspot.com/10388254

git-svn-id: http://src.chromium.org/svn/trunk/src/chrome/browser/policy/proto@140027 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
1 file changed