** 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.
* XHR cross-site access control
** http://dev.w3.org/2006/waf/access-control/
** Missing support for some redirects, but will be fixed in beta2
* TraceMonkey testing via config