support nsIStreamObserver to get rid of an assert in necko.

r=sspitzer

mailnews/base/util/nsMsgProtocol.cpp

@@ -28,7 +28,7 @@
 static NS_DEFINE_CID(kSocketTransportServiceCID, NS_SOCKETTRANSPORTSERVICE_CID);
 static NS_DEFINE_CID(kIOServiceCID, NS_IOSERVICE_CID);
 
-NS_IMPL_ISUPPORTS2(nsMsgProtocol, nsIStreamListener, nsIChannel)
+NS_IMPL_ISUPPORTS3(nsMsgProtocol, nsIStreamListener, nsIStreamObserver, nsIChannel)
 
 nsMsgProtocol::nsMsgProtocol()
 {

mailnews/compose/src/nsURLFetcher.cpp

@@ -57,7 +57,7 @@ nsresult NS_NewURLFetcher(nsURLFetcher ** aInstancePtrResult)
 
 // The following macros actually implement addref, release and 
 // query interface for our component. 
-NS_IMPL_ISUPPORTS(nsURLFetcher, nsCOMTypeInfo<nsIStreamListener>::GetIID());
+NS_IMPL_ISUPPORTS2(nsURLFetcher, nsIStreamListener, nsIStreamObserver);
 
 /* 
  * Inherited methods for nsMimeConverter