Chrome 43 changed the way XMLHttpRequest objects get serialized to JSON. Almost all of the fields as missing now.

xhr.js

var xhr = new XMLHttpRequest()
xhr.open('GET', 'http://requestb.in/155pmaz1')
xhr.onreadystatechange = function () {
  if (xhr.readyState !== 4) return
  var jsonifiedXhr = JSON.parse(JSON.stringify(xhr))
  console.log(Object.keys(jsonifiedXhr))
}
xhr.send()

// Chrome 42
// ["statusText", "status", "responseURL", "response", "responseType", ...]
// Chrome 43
// ["response", "responseText"]