Proposal: iframe/object and :empty pseudo-class

I have to work with an iframe that can be void (the server send an empty
string as content).
Currently, the :empty pseudo-class is useless with iframe, an iframe is
always empty. I must use javascript to display it properly, consisting as
setting class attribute to empty...

The :empty pseudo-class can be set when the request result in a
content-length of 0. Same when the src attribute is empty.
Javascript became useless and a simple styling for iframe and iframe:empty
could do well.