settings-dropdown-menu must set <select>#value after its options change

chrome/test/data/webui/settings/dropdown_menu_tests.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 Suite of tests for settings-dropdown-menu. */
 cr.define('settings_dropdown_menu', function() {
   function registerTests() {
     suite('SettingsDropdownMenu', function() {
       /** @type {SettingsDropdownMenu} */
       var dropdown;
@@ skipping 66 matching lines @@
         return waitUntilDropdownUpdated().then(function() {
           // Initially selected item.
           assertEquals(
               'CCC', selectElement.selectedOptions[0].textContent.trim());
 
           // Selecting an item updates the pref.
           return simulateChangeEvent('a');
         }).then(function() {
           assertEquals('a', dropdown.pref.value);
 
-          // Updating the pref selects an item.
-          dropdown.set('pref.value', 'b');
+          // Item remains selected after updating menu items.
+          var newMenuOptions = dropdown.menuOptions.slice().reverse();
+          dropdown.menuOptions = newMenuOptions;
           return waitUntilDropdownUpdated();
         }).then(function() {
-          assertEquals('b', selectElement.value);
+          assertEquals('AAA',
+              selectElement.selectedOptions[0].textContent.trim());
         });
       });
 
       test('with custom value', function testCustomValue() {
         dropdown.pref = {
           key: 'test.string',
           type: chrome.settingsPrivate.PrefType.STRING,
           value: 'f',
         };
         dropdown.menuOptions =
@@ skipping 14 matching lines @@
         return new Promise(function(resolve) { setTimeout(resolve, timeMs); });
       }
 
       test('delay setting options', function testDelayedOptions() {
         dropdown.pref = {
           key: 'test.number2',
           type: chrome.settingsPrivate.PrefType.NUMBER,
           value: 200,
         };
 
-        console.log('running test');
         return waitForTimeout(100).then(function() {
           return waitUntilDropdownUpdated();
         }).then(function() {
-          assertTrue(dropdown.$.dropdownMenu.disabled);
+          assertTrue(selectElement.disabled);
           assertEquals('SETTINGS_DROPDOWN_NOT_FOUND_ITEM', selectElement.value);
 
           dropdown.menuOptions = [{value: 100, name: 'Option 100'},
                                   {value: 200, name: 'Option 200'},
                                   {value: 300, name: 'Option 300'},
                                   {value: 400, name: 'Option 400'}];
           return waitUntilDropdownUpdated();
         }).then(function() {
           // Dropdown menu enables itself and selects the new menu option
           // correpsonding to the pref value.
-          assertFalse(dropdown.$.dropdownMenu.disabled);
+          assertFalse(selectElement.disabled);
           assertEquals('200', selectElement.value);
+
+          // The "Custom" option should not show up in the dropdown list or be
+          // reachable via type-ahead.
+          var options = selectElement.options;
+          var customOption = assert(options[options.length - 1]);
+          assertTrue(customOption.hidden);
+          assertTrue(customOption.disabled);
         });
       });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });