...since I think that is not always the case.
Seems like we sometimes dispatch first to XHR and then to upload and the current XHR v2 draft says it should happen first upload and then XHR. Don't know if the draft has just changed at some point...
Anyone investigated this? Chromium received the same bug report and going to make it conform to the latest spec. https://code.google.com/p/chromium/issues/detail?id=264609 The reporter said Firefox is following the old spec.
I think this is better tracked by bug 908375 (nearby: bug 918770), since I'm linking to the XHR test suite's send-response-event-order.htm from that bug..