Implement necessary support.

tools/dom/src/native_DOMImplementation.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;
 
 class _Utils {
+  static double dateTimeToDouble(DateTime dateTime) =>
+      dateTime.millisecondsSinceEpoch.toDouble();
+  static DateTime doubleToDateTime(double dateTime) =>
+      new DateTime.fromMillisecondsSinceEpoch(dateTime.toInt());
+
   static List convertToList(List list) {
     // FIXME: [possible optimization]: do not copy the array if Dart_IsArray is fine w/ it.
     final length = list.length;
     List result = new List(length);
     result.setRange(0, length, list);
     return result;
   }
 
   static List convertMapToList(Map map) {
     List result = [];
@@ skipping 89 matching lines @@
   bool get isEmpty => Maps.isEmpty(this);
 }
 
 get _printClosure => (s) {
   try {
     window.console.log(s);
   } catch (_) {
     _Utils.print(s);
   }
 };