XMLHttpRequest progress events

At the moment, Gecko allows adding a single "onprogress" DOMEventListener that's 
notified of download progress.

We would like to make two changes to the progress event setup:

1)  Allow adding progress event listeners via addEventListener, not just via
     setting the onprogress property.  The event name would be "progress".
2)  Allow adding upload progress event listeners via addEventListener.  The
     event name would be "uploadprogress".

The timeline for this would be to make the change in development builds in the 
next several weeks and to ship it hopefully early next year.

Does this seem acceptable?  If not, are there counter-proposals?

-Boris