MD Extensions: Show messages for no extensions, and for no search results

chrome/browser/resources/md_extensions/item_list.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.
 
 cr.define('extensions', function() {
   var ItemList = Polymer({
     is: 'extensions-item-list',
 
     behaviors: [Polymer.NeonAnimatableBehavior, Polymer.IronResizableBehavior],
 
     properties: {
       /** @type {Array<!chrome.developerPrivate.ExtensionInfo>} */
       items: Array,
 
       /** @type {extensions.ItemDelegate} */
       delegate: Object,
 
       inDevMode: {
         type: Boolean,
         value: false,
       },
 
       filter: String,
+
+      /** @private */

[dpapad, 2017/07/07 00:45:04]

Can we annotate what does the array hold? !Array<SomeTypedef>

[scottchen, 2017/07/07 23:08:42]

Done.

+      shownItems_: {
+        type: Array,
+        computed: 'computeShownItems_(items.*, filter)',
+      }
     },
 
     listeners: {
       'list.extension-item-size-changed': 'itemSizeChanged_',
     },
 
     ready: function() {
       /** @type {extensions.AnimationHelper} */
       this.animationHelper = new extensions.AnimationHelper(this, this.$.list);
       this.animationHelper.setEntryAnimations([extensions.Animation.FADE_IN]);
@@ skipping 32 matching lines @@
      * @param {Object} changeRecord The changeRecord for |items|.
      * @param {string} filter The updated filter string.
      * @return {Array<!chrome.developerPrivate.ExtensionInfo>}
      * @private
      */
     computeShownItems_: function(changeRecord, filter) {
       return this.items.filter(function(item) {
         return item.name.toLowerCase().includes(this.filter.toLowerCase());
       }, this);
     },
+
+    isEmpty_: function(length) {
+      return length == 0;
+    }
   });
 
   return {
     ItemList: ItemList,
   };
 });