Fix AudioContext factory constructor.

lib/html/src/dartium_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() => _createAudioContext();
-  static _createAudioContext() native "AudioContext_constructor_Callback";
+  static _createAudioContext([int numberOfChannels,
+                              int numberOfFrames,
+                              int sampleRate])
+      native "AudioContext_constructor_Callback";
 }
 
 class _IDBKeyRangeFactoryProvider {
 
   factory IDBKeyRange.only(/*IDBKey*/ value) =>
       _IDBKeyRangeImpl.only(value);
 
   factory IDBKeyRange.lowerBound(/*IDBKey*/ bound, [bool open = false]) =>
       _IDBKeyRangeImpl.lowerBound(bound, open);
 
@@ skipping 78 matching lines @@
 }
 
 class _WebSocketFactoryProvider {
   factory WebSocket(String url) => _createWebSocket(url);
   static _createWebSocket(String url) native "WebSocket_constructor_Callback";
 }
 
 class _TextFactoryProvider {
   factory Text(String data) => _document.$dom_createTextNode(data);
 }