Adding Element.created constructor

tests/html/custom_elements_test.dart

 // Copyright (c) 2013, 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 custom_elements_test;
 import 'dart:async';
 import 'dart:html';
 import 'package:unittest/html_individual_config.dart';
 import 'package:unittest/unittest.dart';
 import 'utils.dart';
 
 class CustomMixin {
   var mixinMethodCalled;
 
   void mixinMethod() {
     mixinMethodCalled = true;
   }
 }
 
 class CustomType extends HtmlElement with CustomMixin{
   factory CustomType() => null;
+  CustomType.created(): super.created();
+
   bool createdCalled; // = false;
-  void created() {
+  void createdCallback() {
     createdCalled = true;
     customCreatedCount++;
   }
 
   void invokeMixinMethod() {
     mixinMethod();
   }
 }
 
 int customCreatedCount = 0;
@@ skipping 156 matching lines @@
     test('can invoke mixin methods', () {
       var tag = nextTag;
       document.register(tag, CustomType);
 
       var element = new Element.tag(tag);
       element.invokeMixinMethod();
       expect(element.mixinMethodCalled, isTrue);
     });
   });
 }