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