[Chrome OS] Add setting for enabling whitelisting to device policy proto

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;
 
 message DevicePolicyRefreshRateProto {
   // In milliseconds.
   optional int64 policy_refresh_rate = 1;
 }
 
 message UserWhitelistProto {
   repeated string user_whitelist = 1;
 }
 
+message AllowNewUsersProto {
+  // Determines whether we allow arbitrary users to log into the device.
+  // Should default to true.
+  // This interacts with the UserWhitelistProto as follows:
+  // allow_new_users | user_whitelist | user_whitelist_size | anyone can log in
+  //-----------------+----------------+---------------------+------------------
+  //  present, true  | not present    | N/A                 | Yes
+  //-----------------+----------------+---------------------+------------------
+  //  present, true  | present        | >= 0                | Yes
+  //-----------------+----------------+---------------------+------------------
+  //  present, false | not present    | N/A                 | (Broken) Yes
+  //-----------------+----------------+---------------------+------------------
+  //  present, false | present        | 0                   | (Broken) Yes
+  //-----------------+----------------+---------------------+------------------
+  //  present, false | present        | > 0                 | No, W/L enforced
+  //-----------------+----------------+---------------------+------------------
+  //  not present    | not present    | N/A                 | Yes
+  //-----------------+----------------+---------------------+------------------
+  //  not present    | present        | 0                   | Yes
+  //-----------------+----------------+---------------------+------------------
+  //  not present    | present        | > 0                 | No, W/L enforced
+  //-----------------+----------------+---------------------+------------------
+  optional bool allow_new_users = 1;
+}
+
 message GuestModeEnabledProto {
   // Determines if guests are allowed to log in to the device.
   // Should default to true.
   optional bool guest_mode_enabled = 1;
 }
 
 message ShowUserNamesOnSigninProto {
   // Determines if we show pods for existing users on the sign in screen.
   // Should default to true.
   optional bool show_user_names = 1;
@@ skipping 10 matching lines @@
   optional string proxy_server = 2;
   optional string proxy_pac_url = 3;
   optional string proxy_bypass_list = 4;
 }
 
 message ChromeDeviceSettingsProto {
   optional DevicePolicyRefreshRateProto policy_refresh_rate = 1;
   optional UserWhitelistProto user_whitelist = 2;
   optional GuestModeEnabledProto guest_mode_enabled = 3;
   optional DeviceProxySettingsProto device_proxy_settings = 4;
-  optional ShowUserNamesOnSigninProto show_user_names = 5;
-  optional DataRoamingEnabledProto data_roaming_enabled = 6;
+  optional ShowUserNamesOnSigninProto show_user_names = 6;
+  optional DataRoamingEnabledProto data_roaming_enabled = 7;
+  optional AllowNewUsersProto allow_new_users = 8;
 }