MD Settings: Update some dialogs to accept Enter key.

chrome/test/data/webui/settings/startup_urls_page_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.
 
 cr.define('settings_startup_urls_page', function() {
   /**
    * @constructor
    * @implements {settings.StartupUrlsPageBrowserProxy}
    * @extends {settings.TestBrowserProxy}
    */
@@ skipping 165 matching lines @@
     test('AddStartupPage', function() {
       document.body.appendChild(dialog);
       return testProxyCalled('addStartupPage');
     });
 
     test('EditStartupPage', function() {
       dialog.model = createSampleUrlEntry();
       document.body.appendChild(dialog);
       return testProxyCalled('editStartupPage');
     });
+
+    test('Enter key submits', function() {
+      document.body.appendChild(dialog);
+
+      // Input a URL and force validation.
+      var inputElement = dialog.$.url;
+      inputElement.value = 'foo.com';
+      pressSpace(inputElement);
+
+      return browserProxy.whenCalled('validateStartupPage').then(function() {
+        MockInteractions.keyEventOn(
+            inputElement, 'keypress', 13, undefined, 'Enter');
+
+        return browserProxy.whenCalled('addStartupPage');
+      });
+    });
   });
 
   suite('StartupUrlsPage', function() {
     /** @type {?SettingsStartupUrlsPageElement} */
     var page = null;
 
     var browserProxy = null;
 
     setup(function() {
       browserProxy = new TestStartupUrlsPageBrowserProxy();
@@ skipping 140 matching lines @@
     test('Editable', function() {
       assertFalse(!!element.editable);
       assertFalse(!!element.$$('#dots'));
 
       element.editable = true;
       Polymer.dom.flush();
       assertTrue(!!element.$$('#dots'));
     });
   });
 });