FileReader question about ProgressEvent

According to the spec, we will dispatch a progress event for a read method.
But per the "Progress Events 1.0" spec, the attributes "loaded" and "total"
are defined  as "unsigned long".
   interface ProgressEvent : events::Event {
        ...
        readonly attribute unsigned long   loaded;
        readonly attribute unsigned long   total;
        ...

The type "unsigned long" is not enough to represent the file size. Do we
want to update the Progress Event spec to use "unsigned long long"? Or we
could limit the FileReader to only read from the file with size less than
MAX_UINT.


Jian