Updating Polymer to derive from custom elements.

pkg/polymer/test/attr_mustache_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.
 
 import 'dart:async';
 import 'dart:html';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/polymer.dart';
 
 @CustomTag('x-target')
 class XTarget extends PolymerElement {
+  XTarget.created() : super.created();
+
   final Completer _found = new Completer();
   Future get foundSrc => _found.future;
 
   // force an mdv binding
   bind(name, model, path) =>
       TemplateElement.mdvPackage(this).bind(name, model, path);
 
   inserted() {
     testSrcForMustache();
   }
 
-  attributeChanged(name, oldValue) {
+  attributeChanged(name, oldValue, newValue) {
     testSrcForMustache();
     if (attributes[name] == '../testSource') {
       _found.complete();
     }
   }
 
   testSrcForMustache() {
     expect(attributes['src'], isNot(matches(Polymer.bindPattern)),
         reason: 'attribute does not contain {{...}}');
   }
 }
 
 @CustomTag('x-test')
 class XTest extends PolymerElement {
+  XTest.created() : super.created();
+
   @observable var src = 'testSource';
 }
 
 main() {
   useHtmlConfiguration();
 
   test('mustache attributes', () {
     final xtest = document.query('#test').xtag;
     final xtarget = xtest.shadowRoot.query('#target').xtag;
     return xtarget.foundSrc;
   });
 }