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;
 
       /**
        * The <select> used internally by the dropdown menu.
        * @type {HTMLSelectElement}
        */
       var selectElement;
 
+      /**
+       * The "Custom" option in the <select> menu.
+       * @type {HTMLOptionElement}
+       */
+      var customOption;
+
       function waitUntilDropdownUpdated() {
         return new Promise(function(resolve) { dropdown.async(resolve); });
       }
 
       function simulateChangeEvent(value) {
         selectElement.value = value;
         selectElement.dispatchEvent(new CustomEvent('change'));
         return waitUntilDropdownUpdated();
       }
 
       setup(function() {
         PolymerTest.clearBody();
         dropdown = document.createElement('settings-dropdown-menu');
-        selectElement = dropdown.$$('select');
+        selectElement = assert(dropdown.$$('select'));
+        var options = selectElement.options;
+        customOption = assert(options[options.length - 1]);
         document.body.appendChild(dropdown);
       });
 
       test('with number options', function testNumberOptions() {
         dropdown.pref = {
           key: 'test.number',
           type: chrome.settingsPrivate.PrefType.NUMBER,
           value: 100,
         };
         dropdown.menuOptions = [{value: 100, name: 'Option 100'},
@@ skipping 35 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 =
             [{value: 'a', name: 'AAA'},
              {value: 'b', name: 'BBB'},
              {value: 'c', name: 'CCC'},
              {value: 'd', name: 'DDD'}];
 
         return waitUntilDropdownUpdated().then(function() {
           // "Custom" initially selected.
           assertEquals(dropdown.notFoundValue_, selectElement.value);
+          assertEquals('block', getComputedStyle(customOption).display);
+          assertFalse(customOption.disabled);
+
           // Pref should not have changed.
           assertEquals('f', dropdown.pref.value);
         });
       });
 
       function waitForTimeout(timeMs) {
         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.
+          assertEquals('none', getComputedStyle(customOption).display);
+          assertTrue(customOption.disabled);
         });
       });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });