Added back childNodes and getAttribute and setAttribute.

tools/dom/src/AttributeMap.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.
 
 part of html;
 
 abstract class _AttributeMap implements Map<String, String> {
   final Element _element;
 
   _AttributeMap(this._element);
@@ skipping 74 matching lines @@
  */
 class _ElementAttributeMap extends _AttributeMap {
 
   _ElementAttributeMap(Element element): super(element);
 
   bool containsKey(String key) {
     return _element._hasAttribute(key);
   }
 
   String operator [](String key) {
-    return _element._getAttribute(key);
+    return _element.getAttribute(key);
   }
 
   void operator []=(String key, String value) {
-    _element._setAttribute(key, value);
+    _element.setAttribute(key, value);
   }
 
   String remove(String key) {
-    String value = _element._getAttribute(key);
+    String value = _element.getAttribute(key);
     _element._removeAttribute(key);
     return value;
   }
 
   /**
    * The number of {key, value} pairs in the map.
    */
   int get length {
     return keys.length;
   }
 
   bool _matches(Node node) => node._namespaceUri == null;
 }
 
 /**
  * Wrapper to expose namespaced attributes as a typed map.
  */
 class _NamespacedAttributeMap extends _AttributeMap {
 
   final String _namespace;
 
   _NamespacedAttributeMap(Element element, this._namespace): super(element);
 
   bool containsKey(String key) {
     return _element._hasAttributeNS(_namespace, key);
   }
 
   String operator [](String key) {
-    return _element._getAttributeNS(_namespace, key);
+    return _element.getAttributeNS(_namespace, key);
   }
 
   void operator []=(String key, String value) {
-    _element._setAttributeNS(_namespace, key, value);
+    _element.setAttributeNS(_namespace, key, value);
   }
 
   String remove(String key) {
     String value = this[key];
     _element._removeAttributeNS(_namespace, key);
     return value;
   }
 
   /**
    * The number of {key, value} pairs in the map.
@@ skipping 74 matching lines @@
   // TODO: Use lazy iterator when it is available on Map.
   bool get isEmpty => length == 0;
 
   bool get isNotEmpty => !isEmpty;
 
   // Helpers.
   String _attr(String key) => 'data-$key';
   bool _matches(String key) => key.startsWith('data-');
   String _strip(String key) => key.substring(5);
 }