Updating Polymer to derive from custom elements.

pkg/polymer/test/prop_attr_reflection_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:html';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/platform.dart' as Platform;
 import 'package:polymer/polymer.dart';
 
 class XFoo extends PolymerElement {
+  XFoo.created() : super.created();
+
   @observable var foo = '';
   @observable String baz = '';
 }
 
 class XBar extends XFoo {
+  XBar.created() : super.created();
+
   @observable int zot = 3;
   @observable bool zim = false;
   @observable String str = 'str';
   @observable Object obj;
 }
 
 class XCompose extends PolymerElement {
+  XCompose.created() : super.created();
+
   @observable bool zim = false;
 }
 
 main() {
   useHtmlConfiguration();
 
   // Most tests use @CustomTag, here we test out the impertive register:
   Polymer.register('x-foo', XFoo);
   Polymer.register('x-bar', XBar);
   Polymer.register('x-compose', XCompose);
@@ skipping 67 matching lines @@
             Platform.endOfMicrotask(expectAsync0(() {
               expect(xbar.attributes['obj'], objAttr, reason:
                   'do not reflect property with default type of object');
             }));
           }));
         }));
       }));
     }));
   });
 }