Fix all remaining print preview closure compiler errors

chrome/browser/resources/print_preview/data/destination_store.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.
 
 cr.define('print_preview', function() {
   'use strict';
 
   /**
    * A data store that stores destinations and dispatches events when the data
    * store changes.
@@ skipping 513 matching lines @@
     mediaSize.option = categoryStandardNA;
     mediaSize.option.push(...categoryStandardCN, ...categoryStandardISO,
         ...categoryStandardJP, ...categoryStandardMisc, ...categoryCustom);
     return capabilities;
   };
 
   DestinationStore.prototype = {
     __proto__: cr.EventTarget.prototype,
 
     /**
-     * @param {string=} opt_account Account to filter destinations by. When
-     *     omitted, all destinations are returned.
+     * @param {?string=} opt_account Account to filter destinations by. When
+     *     null or omitted, all destinations are returned.
      * @return {!Array<!print_preview.Destination>} List of destinations
      *     accessible by the {@code account}.
      */
     destinations: function(opt_account) {
       if (opt_account) {
         return this.destinations_.filter(function(destination) {
           return !destination.account || destination.account == opt_account;
         });
       }
       return this.destinations_.slice(0);
@@ skipping 1150 matching lines @@
       return this.getDestinationKey_(
           destination.origin, destination.id, destination.account);
     }
   };
 
   // Export
   return {
     DestinationStore: DestinationStore
   };
 });