Rate SVG resources to CSP directive

Hi All,

my name is Renata Hodovan and I work on WebKit. I'd like to add external 
resource support to SVGUseElement. During this I faced a problem. We 
should rate this new resource under a Content-Security-Policy directive. 
So the question is which one should it belong to? Currently I added it 
to the image directive. Is it right?
You can find the bug here: https://bugs.webkit.org/show_bug.cgi?id=12499

Thanks in advance,
Reni