[MD settings] specify @override on created, ready, and attached

chrome/browser/resources/settings/site_settings/website_usage_private_api.js

 // Copyright 2016 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() {
 'use strict';
 
 Polymer({
   is: 'website-usage-private-api',
 
   properties: {
     /**
      * The amount of data used by the given website.
      */
     websiteDataUsage: {
       type: String,
       notify: true,
     },
 
     /**
      * The type of data used by the given website.
      */
     websiteStorageType: {
       type: Number,
       notify: true,
     },
   },
 
+  /** @override */
   attached: function() {
     settings.WebsiteUsagePrivateApi.websiteUsagePolymerInstance = this;
   },
 
   /** @param {string} host */
   fetchUsageTotal: function(host) {
     settings.WebsiteUsagePrivateApi.fetchUsageTotal(host);
   },
 
   /**
@@ skipping 75 matching lines @@
 
     instance.notifyUsageDeleted(origin);
   };
 
   return { websiteUsagePolymerInstance: websiteUsagePolymerInstance,
            fetchUsageTotal: fetchUsageTotal,
            returnUsageTotal: returnUsageTotal,
            clearUsage: clearUsage,
            onUsageCleared: onUsageCleared, };
 });