in Warning in 3.2, suggest changing "Instead, a callback is to be used." to read "Instead, a callback SHOULD be used."
There was a reason in my mind why I used that wording when I wrote it, but I don't remember it now. Anyway, fixed now.
Are warnings not supposed to be non-normative?
Warnings are meant to be normative: http://dev.w3.org/2006/webapi/WebIDL/#conventions