Convert DOM and HTML frog to dart2js.

lib/dom/src/frog_FactoryProviders.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.
-
-class _AudioContextFactoryProvider {
-
-  factory AudioContext() native '''
-    var constructor = window.AudioContext || window.webkitAudioContext;
-    return new constructor();
-''';
-}
-
-class _WebKitPointFactoryProvider {
-
-  factory WebKitPoint(num x, num y) native '''return new WebKitPoint(x, y);''';
-}
-
-class _WebSocketFactoryProvider {
-
-  factory WebSocket(String url) native '''return new WebSocket(url);''';
-}