Fix RtcDataChannel for Firefox nightly

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json' as json;
@@ skipping 18411 matching lines @@
 }
 // 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.
 
 
 @DocsEditable
 @DomName('RTCDataChannel')
 // http://dev.w3.org/2011/webrtc/editor/webrtc.html#idl-def-RTCDataChannel
 @Experimental
-class RtcDataChannel extends EventTarget native "RTCDataChannel" {
+class RtcDataChannel extends EventTarget native "RTCDataChannel,DataChannel" {
 
   @DomName('RTCDataChannel.closeEvent')
   @DocsEditable
   static const EventStreamProvider<Event> closeEvent = const EventStreamProvider<Event>('close');
 
   @DomName('RTCDataChannel.errorEvent')
   @DocsEditable
   static const EventStreamProvider<Event> errorEvent = const EventStreamProvider<Event>('error');
 
   @DomName('RTCDataChannel.messageEvent')
@@ skipping 11411 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }