[css3-2d-transforms] convertPoint* functions when node isn't an element in a document

The convertPointFromPageToNode and convertPointFromNodeToPage functions  
take a Node as their first parameter. Since there are at least 12 node  
types this means they don't just accept elements, but also things like  
attribute nodes and comment nodes, for which the function descriptions  
don't really make sense. It's also possible to have a node that's not part  
of a document tree. The specification should say what happens in these  
cases.

A related suggestion is to have these functions on an extension to the  
Element interface instead (though that still leaves the case of e.g.  
document.createElement('div').convertPoint[...]).

-- 
Øyvind Stenhaug
Core Norway, Opera Software ASA