webui fixes for 0.8.9

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 '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 extends CustomElement {
@@ skipping 300 matching lines @@
  * traversal.
  */
 bool useShadowDom = false;
 
 bool get _realShadowRoot => useShadowDom && ShadowRoot.supported;
 
 /**
  * Set this to the [Element] to be used as the root for the Web UI app.
  */
 Element webUIRoot = document.body;