Make OptionElement construtor arguments named optional parameters.

tests/html/selectelement_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library selectelement_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 main() {
   useHtmlConfiguration();
 
   test('selectedOptions', () {
     var element = new SelectElement();
     element.multiple = false;
     var options = [
       new OptionElement(),
       new DivElement(),
-      new OptionElement('data', 'two', false, true),
+      new OptionElement(data: 'data', value: 'two', defaultSelected: false,
+          selected: true),
       new DivElement(),
-      new OptionElement('data', 'two', false, true),
+      new OptionElement(data: 'data', value: 'two', defaultSelected: false,
+          selected: true),
       new OptionElement(),
     ];
     element.children.addAll(options);
     expect(element.selectedOptions.length, 1);
     expect(element.selectedOptions[0], equals(options[4]));
   });
 
   test('multiple selectedOptions', () {
     var element = new SelectElement();
     element.multiple = true;
     var options = [
       new OptionElement(),
       new DivElement(),
-      new OptionElement('data', 'two', false, true),
+      new OptionElement(data: 'data', value: 'two', defaultSelected: false,
+          selected: true),
       new DivElement(),
-      new OptionElement('data', 'two', false, true),
+      new OptionElement(data: 'data', value: 'two', defaultSelected: false,
+          selected: true),
       new OptionElement(),
     ];
     element.children.addAll(options);
     expect(element.selectedOptions.length, 2);
     expect(element.selectedOptions[0], equals(options[2]));
     expect(element.selectedOptions[1], equals(options[4]));
   });
 
   test('options', () {
     var element = new SelectElement();
     var options = [
       new OptionElement(),
-      new OptionElement('data', 'two', false, true),
-      new OptionElement('data', 'two', false, true),
+      new OptionElement(data: 'data', value: 'two', defaultSelected: false,
+          selected: true),
+      new OptionElement(data: 'data', value: 'two', defaultSelected: false,
+          selected: true),
       new OptionElement(),
     ];
     element.children.addAll(options);
     // Use last to make sure that the list was correctly wrapped.
     expect(element.options.last, equals(options[3]));
   });
 
   test('optgroup', () {
     var element = new Element.html(
       '<select>'
         '<option>1</option>'
         '<optgroup>'
           '<option>2</option>'
         '</optgroup>'
       '</select>');
 
     expect(element.options.length, 2);
     element.selectedIndex = 1;
 
     var optGroup = element.children[1];
     expect(optGroup is OptGroupElement, isTrue);
     expect(optGroup.children.single.selected, isTrue);
     expect(element.selectedOptions, optGroup.children);
   });
 }