[XBL] Event Inteface is not referenced

In sections 3.1, 3.5, 7.5, you talk about an "Event interface" but you 
don't provide any IDL or a reference to that interface (i know you are 
talking about DOM3, you don't make this clear in the document... 
however, you do make it clear for other event types, such as 
MutationEvent, TextEvent , KeyboardEvent etc...).