anchor.diff:      headers._finalize();
   
       // Write headers.
  -    headers._write(this);
  +    headers._write(_ioSink);
       writeCRLF();
     }
   }
  
positive.code: 
    void _writeHeaders() {
      if (_headersWritten) return;
      bool _tmpIgnoreBody = _ignoreBody;
      _ignoreBody = false;
      _headersWritten = true;
      _writeHeader();
      _ignoreBody = _tmpIgnoreBody;
      if (_ignoreBody) {
        _ioSink.close();
        return;
  
negative.code:   }
  
    void _writeHeader() {
      writeSP() => _ioSink.add([_CharCode.SP]);
      writeCRLF() => _ioSink.add([_CharCode.CR, _CharCode.LF]);
  
      _ioSink.addString(method);
      writeSP();
      // Send the path for direct connections and the whole URL for
      // proxy connections.
  