anchor.diff:  part of dtmark;
   
  +/**
  + * Wrapper around a WebAudio AudioContext which is used by DTMark audio classes.
  + */
   class AudioEngine {
   
     WebAudio.AudioContext ctx;
  
positive.code: }
  
  /**
   * Audio source that is streamed in while playing using AudioElement instead of being preloaded.
   */
  class AudioStream extends PlayableAudio {
  
  
negative.code: 
    double get volume => _gain.gain.value;
  
    static bool _webAudioSupport = null;
    /**
     * Whether or not the browser supports WebAudio. Applications should
     * gracefully handle a lack of WebAudio support by not playing
     * audio, instead of simply crashing. However, it is likely
     * that any browser supporting WebGL also supports WebAudio.
     */
    static bool get webAudioSupport {
      if (_webAudioSupport == null) {
        var jswindow = new JsObject.fromBrowserObject(window);
        _webAudioSupport = jswindow.hasProperty("AudioContext") ||
          jswindow.hasProperty("webkitAudioContext");
      }
      return _webAudioSupport;
    }
  
  }
  
  /**
  