Make AudioContext work in iOS 7.

sdk/lib/web_audio/dart2js/web_audio_dart2js.dart

 /**
  * High-fidelity audio programming in the browser.
  */
 library dart.dom.web_audio;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide deprecated;
 import 'dart:html';
 import 'dart:html_common';
@@ skipping 211 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.
 
 
 @DomName('AudioContext')
 // https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#AudioContext-section
 @Experimental()
-class AudioContext extends EventTarget native "AudioContext" {
+class AudioContext extends EventTarget native "AudioContext,webkitAudioContext" {
   // To suppress missing implicit constructor warnings.
   factory AudioContext._() { throw new UnsupportedError("Not supported"); }
 
   @DomName('AudioContext.completeEvent')
   @DocsEditable()
   static const EventStreamProvider<Event> completeEvent = const EventStreamProvider<Event>('complete');
 
   /// Checks if this type is supported on the current platform.
   static bool get supported => JS('bool', '!!(window.AudioContext || window.webkitAudioContext)');
 
@@ skipping 887 matching lines @@
   factory WaveShaperNode._() { throw new UnsupportedError("Not supported"); }
 
   @DomName('WaveShaperNode.curve')
   @DocsEditable()
   Float32List curve;
 
   @DomName('WaveShaperNode.oversample')
   @DocsEditable()
   String oversample;
 }