Implement a policy to autologin a public account.

chrome/browser/chromeos/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 213 matching lines @@
   // Policy-configured device-local accounts are on the same domain that the
   // device is enrolled to. In contrast to RFC 5322 (which is more restrictive),
   // the local part may contain any characters other than '@'.
   optional string id = 1;
 }
 
 message DeviceLocalAccountsProto {
   // The list of device-local accounts (i.e. accounts without an associated
   // cloud-backed profile) that are available on the device.
   repeated DeviceLocalAccountInfoProto account = 1;
+
+  // The identifier of the device-local account to which the device
+  // should be logged in automatically.  Should be equal to one of the
+  // ids in DeviceLocalAccountInfoProto.
+  optional string auto_login_id = 2;
+
+  // The amount of time, in milliseconds, that should elapse at the signin
+  // screen without user interaction before automatically logging in.
+  optional int64 auto_login_delay = 3;
 }
 
 message AllowRedeemChromeOsRegistrationOffersProto {
   // Chrome OS Registration service provides way for chromeos device users
   // to redeem electronic offers provided by service provider.
   // This value determines if users are allowed to redeem offers through
   // Chrome OS Registration service.
   optional bool allow_redeem_offers = 1 [default = true];
 }
 
@@ skipping 21 matching lines @@
   optional ForcedLogoutTimeoutsProto forced_logout_timeouts = 15;
   optional ScreenSaverProto login_screen_saver = 16;
   optional AutoUpdateSettingsProto auto_update_settings = 17;
   optional StartUpUrlsProto start_up_urls = 18;
   optional PinnedAppsProto pinned_apps = 19;
   optional SystemTimezoneProto system_timezone = 20;
   optional DeviceLocalAccountsProto device_local_accounts = 21;
   optional AllowRedeemChromeOsRegistrationOffersProto allow_redeem_offers = 22;
   optional StartUpFlagsProto start_up_flags = 23;
 }