Add a device policy for specifying the release channel.

chrome/browser/policy/proto/chrome_device_policy.proto

 // Copyright (c) 2011 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 57 matching lines @@
 }
 
 message CameraEnabledProto {
   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;
+}
+
 message ChromeDeviceSettingsProto {
   optional DevicePolicyRefreshRateProto device_policy_refresh_rate = 1;
   optional UserWhitelistProto user_whitelist = 2;
   optional GuestModeEnabledProto guest_mode_enabled = 3;
   optional DeviceProxySettingsProto device_proxy_settings = 4;
   optional CameraEnabledProto camera_enabled = 5;
   optional ShowUserNamesOnSigninProto show_user_names = 6;
   optional DataRoamingEnabledProto data_roaming_enabled = 7;
   optional AllowNewUsersProto allow_new_users = 8;
   optional MetricsEnabledProto metrics_enabled = 9;
+  optional ReleaseChannelProto release_channel = 10;
 }