title: Access file name from XHR event
body: <p>I am using XMLHttpRequest to upload a file. On the event completion I would like to have the filename - the server (AWS S3) returns no response with that info.  What is the proper way to access this file name?  If I overload XMLHttpRequest with xhr.filename = 'abc.jpg' I can acces it in event but seems a bit unclean. I tried setting a request header but I dont see a way to access that in the returned event. Is there a better way (and yes I can reformat my scope etc but I am specifically interested in accessing the file name in the returned event.</p>
  
  <pre><code>function upload() {
  
    var xhr = new XMLHttpRequest();
    xhr.upload.addEventListener("progress", uploadProgress, false);
    xhr.addEventListener("load", uploadComplete, false);
    xhr.addEventListener("error", uploadFailed, false);
    xhr.addEventListener("abort", uploadCanceled, false);
  
    xhr.setRequestHeader("X-File-Name", file.name);  // how to access this?
    xhr.filename = file.name; // works but seems a bit unclean imo
  
    scope.progressVisible = true;
    xhr.send(data);
  
  
    }, function(err) {
      console.log(err);
    });
  };
  
  
  function uploadComplete(evt) {
     // I want the file name here as part of this function's parameters (i.e. evt - doesn't seem to return anymore params than that)
  }
  </code></pre>