nsIContentPolicy - Archive of obsolete content
63 introduced gecko 1.0 inherits from: nsicontentpolicybase last changed in gecko 42 (firefox 42 / thunderbird 42 / seamonkey 2.39) you can observe content that is being loaded into your browser by implementing nsicontentpolicy.
... warning: do not block the caller in your implementations of shouldload() or shouldprocess() (for example, by launching a dialog to prompt the user for something).") note: in reality, much of this interface is defined in the nsicontentpolicybase interface, but for now is documented here until someone has time to split things up.

nsIIOService
any of the content types defined in nsicontentpolicybase.idl.