Bug 1299642 - Fix docshell errors when breaking chrome -> chrome leaks. r=ted

It appears the lambda function passed to waitForFocus goes out of
scope when the window is closed. Just pass in SimpleTest.finish
directly instead.

docshell/test/chrome/docshell_helpers.js

@@ -362,9 +362,7 @@ function finish() {
   ww.registerNotification(function(subject, topic, data) {
     if (topic == "domwindowclosed") {
       ww.unregisterNotification(arguments.callee);
-      SimpleTest.waitForFocus(function() {
-        SimpleTest.finish();
-      }, opener);
+      SimpleTest.waitForFocus(SimpleTest.finish, opener);
     }
   });