use custom_element pkg

lib/web_ui.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.
 
 /**
  * This library exports all of the commonly used functions and types for
  * building UI's. It is equivalent to the following imports:
  *
  *     import 'package:web_ui/observe.dart';
  *     import 'package:web_ui/safe_html.dart';
  *     import 'package:web_ui/templating.dart';
  *     import 'package:web_ui/watcher.dart';
  *     import 'package:web_ui/web_ui.dart' show WebComponent;
  *
  * Note that the [WebComponent] base class is defined in this library.
  *
  * See this article for more information:
  * <http://www.dartlang.org/articles/dart-web-components/>.
  */
 library web_ui;
 
 export 'observe.dart';
 export 'safe_html.dart';
 export 'templating.dart';
 export 'watcher.dart';
 
 import 'dart:async';
 import 'dart:html';
-import 'dart:mirrors' show reflect;
+import 'package:custom_element/custom_element.dart' show CustomElement;
 import 'package:meta/meta.dart';
 
 /**
  * The base class for all Dart web components. In addition to the [Element]
  * interface, it also provides lifecycle methods:
  * - [created]
  * - [inserted]
  * - [attributeChanged]
  * - [removed]
  */
-abstract class WebComponent implements Element {
+abstract class WebComponent extends CustomElement {
   /** The web component element wrapped by this class. */
   Element _host;
   List _shadowRoots;
 
   /**
    * Shadow roots generated by dwc for each custom element, indexed by the
    * custom element tag name.
    */
   Map<String, dynamic> _generatedRoots = {};
 
@@ skipping 251 matching lines @@
 
   /** Distribute the [nodes] in place of an existing [insertionPoint]. */
   static void _distribute(Element insertionPoint, Iterable<Node> nodes) {
     assert(_isInsertionPoint(insertionPoint));
     insertionPoint.parent.insertAllBefore(nodes, insertionPoint);
     insertionPoint.remove();
   }
 
   // TODO(jmesserly): rename "created" to "onCreated".
   void onCreated() => created();
-
-  /** The rest of the [Element] API is handled by [host]. */
-  dynamic noSuchMethod(Invocation m) => reflect(host).delegate(m);
 }
 
 /**
  * Maps CSS selectors (class and) to a mangled name and maps x-component name
  * to [is='x-component'].
  */
 class ScopedCssMapper {
   final Map<String, String> _mapping;
 
   ScopedCssMapper(this._mapping);
@@ skipping 14 matching lines @@
 }
 
 /**
  * Set this to true to use native Shadow DOM if it is supported.
  * Note that this will change behavior of [WebComponent] APIs for tree
  * traversal.
  */
 bool useShadowDom = false;
 
 bool get _realShadowRoot => useShadowDom && ShadowRoot.supported;