buffet: Grant buffet group access to buffet DBus API.

BUG=chromium:434766
TEST=manual

Change-Id: I28bad564fdc1da04b3e80b2e622904c08ef0172d
Reviewed-on: https://chromium-review.googlesource.com/230851
Tested-by: Anton Muhin <antonm@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Commit-Queue: Anton Muhin <antonm@chromium.org>

buffet/etc/dbus-1/org.chromium.Buffet.conf

diff --git a/buffet/etc/dbus-1/org.chromium.Buffet.conf b/buffet/etc/dbus-1/org.chromium.Buffet.conf
index aca550f..34e2bdc 100644
--- a/buffet/etc/dbus-1/org.chromium.Buffet.conf
+++ b/buffet/etc/dbus-1/org.chromium.Buffet.conf
@@ -6,9 +6,12 @@
     <allow send_destination="org.chromium.Buffet" />
   </policy>
 
+  <policy group="buffet">
+    <allow send_destination="org.chromium.Buffet" />
+  </policy>
+
   <policy user="buffet">
     <allow own="org.chromium.Buffet" />
-    <allow send_destination="org.chromium.Buffet" />
   </policy>
 
   <policy context="default">