anchor.diff:    }
   
     Encoding get encoding {
  +    if (_encodingSet && _headersWritten) {
  +      return _encoding;
  +    }
       var charset;
       if (headers.contentType != null && headers.contentType.charset != null) {
         charset = headers.contentType.charset;
  
positive.code:       return this;
      }
      if (_headersWritten) return new Future.value(this);
      _encoding = encoding;
      _headersWritten = true;
      Future drainFuture;
      bool isServerSide = this is _HttpResponse;
  
negative.code:   // requests and in error handling.
    bool _ignoreBody = false;
    bool _headersWritten = false;
    bool _encodingSet = false;
  
    final Uri _uri;
    final _HttpOutgoing _outgoing;
  