title: xhr.upload.onprogress doesn't work
body: <p>Everything in the following code will work, except it will never fire the xhr.upload.onprogress event.</p>
  
  <pre><code>$(function(){
  
      var xhr;
  
      $("#submit").click(function(){
          var formData = new FormData();
          formData.append("myFile", document.getElementById("myFileField").files[0]);
          xhr = new XMLHttpRequest();
          xhr.open("POST", "./test.php", true);
          xhr.send(formData);
  
          xhr.onreadystatechange = function(){
              if(xhr.readyState === 4 &amp;&amp; xhr.status === 200){
                  console.log(xhr.responseText);              
              }
          }
  
          xhr.upload.onprogress = function(e) {
             // it will never come inside here
          }
      });
  }); 
  </code></pre>