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

chrome/test/data/webui/extensions/extension_item_list_test.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.
 
 /** @fileoverview Suite of tests for extension-item. */
 cr.define('extension_item_list_tests', function() {
   /** @enum {string} */
   var TestNames = {
     ItemListFiltering: 'item list filtering',
+    ItemListNoItemsMsg: 'empty item list',
+    ItemListNoSearchResultsMsg: 'empty item list filtering results',
   };
 
   function registerTests() {
     suite('ExtensionItemListTest', function() {
       /** @type {extensions.ItemList} */
       var itemList;
+      var testVisible;
 
       suiteSetup(function() {
         return PolymerTest.importHtml('chrome://extensions/item-list.html');
       });
 
       // Initialize an extension item before each test.
       setup(function() {
         PolymerTest.clearBody();
         itemList = new extensions.ItemList();
+        testVisible = extension_test_util.testVisible.bind(null, itemList);
+
         var createExt = extension_test_util.createExtensionInfo;
         var items =
             [createExt({name: 'Alpha', id: 'a'.repeat(32)}),
              createExt({name: 'Bravo', id: 'b'.repeat(32)}),
              createExt({name: 'Charlie', id: 'c'.repeat(32)})];
         itemList.items = items;
         itemList.filter = '';
         document.body.appendChild(itemList);
       });
 
@@ skipping 18 matching lines @@
         itemList.filter = 'lph';
         expectEquals(1, ironList.items.length);
         expectEquals('Alpha', ironList.items[0].name);
         // Test string with no matching items.
         itemList.filter = 'z';
         expectEquals(0, ironList.items.length);
         // A filter of '' should reset to show all items.
         itemList.filter = '';
         expectEquals(3, ironList.items.length);
       });
+
+      test(assert(TestNames.ItemListNoItemsMsg), function() {
+        testVisible('#no-items', false);
+        testVisible('#no-search-results', false);
+
+        itemList.items = [];
+        testVisible('#no-items', true);
+        testVisible('#no-search-results', false);
+      });
+
+      test(assert(TestNames.ItemListNoSearchResultsMsg), function() {
+        testVisible('#no-items', false);
+        testVisible('#no-search-results', false);
+
+        itemList.filter = 'non-existent name';
+        testVisible('#no-items', false);
+        testVisible('#no-search-results', true);
+      });
     });
   }
 
   return {
     registerTests: registerTests,
     TestNames: TestNames,
   };
 });