nsIHttpEventSink

 Implement this interface to receive control over various HTTP events.  The
 HTTP channel will try to get this interface from its notificationCallbacks
 attribute, and if it doesn't find it there it will look for it from its
 loadGroup's notificationCallbacks attribute.

 These methods are called before onStartRequest, and should be handled
 SYNCHRONOUSLY.

 @deprecated Newly written code should use nsIChannelEventSink instead of this
 interface.
[scriptable, uuid(9475a6af-6352-4251-90f9-d65b1cd2ea15)]
interface nsIHttpEventSink : nsISupports

Methods

 Called when a redirect occurs due to a HTTP response like 302.  The
 redirection may be to a non-http channel.

 @return failure cancels redirect
void onRedirect(in nsIHttpChannel httpChannel, in nsIChannel newChannel)