** all those events are fired on the XHR.upload property and fire for the uploading
** Demo of new features: http://mozilla.pettay.fi/xhr_upload/xhr_upload_demo.html
** Could do this with the old uploadprogress event, but was non-standard, gave bad data about sizes (included headers, etc) and was tricky to use for starts and stops.
* TraceMonkey testing via config