fix a typo in settings.js

chrome/browser/resources/settings/settings.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'cr-settings' is the main MD-Settings element, combining the UI and models.
  *
  * Example:
  *
  *    <cr-settings></cr-settings>
  *
  * @group Chrome Settings Elements
  * @element cr-settings
  */
 Polymer({
   is: 'cr-settings',
 
-  properties {
+  properties: {
     /**
      * The CrSettingsPrefsElement used throughout the app.
      * @private {!CrSettingsPrefsElement}
      */
     prefs_: {
       type: Object,
       value: function() { return this.$.prefs; },
       notify: true,
     }
   },
 });