anchor.diff:  class LongPollChannel extends AMFChannel {
     
     static const List<String> _LONG_POLLING = const <String>['long-polling'];
  +  static const Map<String, String> _HEADERS = const <String, String>{'Content-Type': 'application/x-amf'};
     
     final String endPoint;
     final String url;
  
positive.code:       mimeType: 'application/x-amf',
        sendData: new AMF3Output([CM], messageOutputWriter).writeObject(),
        responseType: 'arraybuffer',
        requestHeaders: <String, String>{'Content-Type': 'application/x-amf'}
      );
      
      if (request.response is ByteBuffer)
  
negative.code:       mimeType: 'application/x-amf',
        sendData: new AMF3Output([CM], messageOutputWriter).writeObject(),
        responseType: 'arraybuffer',
        requestHeaders: _HEADERS
      );
      
      if (request.response is ByteBuffer) {
  