Add a lock to the managed user settings page and require authentication for unlocking.

chrome/browser/resources/managed_user_passphrase_dialog.js

+// 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.
+
+function load() {
+  $('unlock_passphrase_button').onclick = function(event) {
+    if ($('passphrase_entry').value == '') {
+      return;
+    }
+    chrome.send('checkPassphrase', [$('passphrase_entry').value]);
+    $('passphrase_entry').value = '';
+  }
+  $('cancel_passphrase_button').onclick = function(event) {
+    chrome.send('DialogClose');
+  }
+}
+
+function passphraseCorrect() {
+  chrome.send('DialogClose', ['correct']);
+}
+
+function passphraseIncorrect() {
+  $('incorrect_passphrase_warning').style.visibility = 'visible';
+}
+
+// Add handlers to HTML elements.
+window.addEventListener('DOMContentLoaded', load);