Bug 805063 - Fix hang in crashtest for bug 791330. r=ekr

dom/media/tests/crashtests/791330.html

@@ -17,8 +17,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=791330
 
       navigator.mozGetUserMedia({audio: true, fake: true}, function (stream) {
         pc.addStream(stream);
-        pc.createOffer(function (offer) {
-        }, finish);
+        pc.createOffer(function (offer) {});
+        finish();
       }, function () {});
     }
   </script>