anchor.diff:      }
   
       var headers = {
  +        'user-agent' : USER_AGENT_STRING,
           'content-type' : _uploadMedia.contentType,
           'content-length' : '${chunk.length}',
           'content-range' :
  
positive.code:       var bodyStream = uploadMedia.stream;
        var request = new RequestImpl(method, uri, bodyStream);
        request.headers.addAll({
          'content-type' : uploadMedia.contentType,
          'content-length' : '${uploadMedia.length}'
        });
  
negative.code: 
      var request = new RequestImpl(_method, _uri, bodyStream);
      request.headers.addAll({
        'user-agent' : USER_AGENT_STRING,
        'content-type' : CONTENT_TYPE_JSON_UTF8,
        'content-length' : '$length',
        'x-upload-content-type' : _uploadMedia.contentType,
  