[WebIDL] Assigning to constants

What should happen when you assign something to a constant? e.g.:

    Node.ELEMENT_NODE = 'Hello world';

Web IDL doesn't say, AFAICT. Firefox and Opera allow the assignment. In  
WebKit it silently fails. I had expected an exception to be thrown, just  
like for readonly attributes.

It'd be good if this was defined.

-- 
Simon Pieters
Opera Software