anchor.diff:  
       var fp = new FileProgress(_queue.removeAt(0));
   
  -    uploadStrategy.uploadFile(fp, progress:(num pct) => fp.progress = 0.5 + pct / 2);
  -    _startUpload();
  +    uploadStrategy.uploadFile(fp, progress:(num n)=>fp.progress = n).then((_)=>_startUpload());
  +
     }
   
     Stream<FileUploader> get onProgress => _progress_stream;
  
positive.code:         c(null);
        }
      });
    }
  
  }
  
negative.code: 
    }
  
    Future<Response<String>> uploadFile(FileProgress fileProgress, {void progress(num pct):null}) {
      var completer = new Completer();
      var reader = new FileReader();
      reader.onLoadEnd.listen((_) {
        fileProgress.previewPath = reader.result;
  