Add a new policy to allow for release channel delegation.

chrome/browser/policy/proto/chrome_device_policy.proto

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package enterprise_management;
 
@@ skipping 60 matching lines @@
   optional bool camera_enabled = 1;
 }
 
 message MetricsEnabledProto {
   optional bool metrics_enabled = 1;
 }
 
 message ReleaseChannelProto {
   // One of "stable-channel", "beta-channel", or "dev-channel"
   optional string release_channel = 1;
+
+  // If |user_delegated| is set to true and the |release_channel| field is not
+  // set or left empty, the user can select the channel. If the
+  // |release_channel| is specified it will always override users choice!
+  optional bool release_channel_delegated = 2;
 }
 
 message DeviceOpenNetworkConfigurationProto {
   // The network configuration blob. This is a JSON string as specified by ONC.
   optional string open_network_configuration = 1;
 }
 
 // Policies to turn on portions of the device status reports.
 message DeviceReportingProto {
   optional bool report_version_info = 1;
@@ skipping 54 matching lines @@
   optional AllowNewUsersProto allow_new_users = 8;
   optional MetricsEnabledProto metrics_enabled = 9;
   optional ReleaseChannelProto release_channel = 10;
   optional DeviceOpenNetworkConfigurationProto open_network_configuration = 11;
   optional DeviceReportingProto device_reporting = 12;
   optional EphemeralUsersEnabledProto ephemeral_users_enabled = 13;
   optional AppPackProto app_pack = 14;
   optional ForcedLogoutTimeoutsProto forced_logout_timeouts = 15;
   optional ScreenSaverProto login_screen_saver = 16;
 }