Bug 949227 - browser_bug609700.js | Found an unexpected tab at the end of test run: about:blank, r=gavin

--HG--
extra : rebase_source : 8d8713551121c58a2cfc5a58516ea1f7a16f1d61

browser/base/content/test/general/browser_bug609700.js

@@ -7,8 +7,7 @@ function test() {
 
       ok(true, "duplicateTabIn opened a new window");
 
-      aSubject.addEventListener("load", function () {
-        aSubject.removeEventListener("load", arguments.callee, false);
+      whenDelayedStartupFinished(aSubject, function () {
         executeSoon(function () {
           aSubject.close();
           finish();