[webappsec] do we want a way to hash data: and blob: uris?

Just had a chat with Marcos on how manifests want to use CSP.

It came up that while data;, blob:, etc. are effectively
unsafe-inline, we don't have a way to treat them with hash-source.  If
I want to allow a specific data: uri but not all data: uris, I need to
repeat the whole blob in my CSP.

Is it worthwhile (for v.Next) to specify a way to take the hash of
GUID-type uris?

-Brad