Bug 579540: Add a longer timeout to browser_bug553455.js. r=sdwilsh, a=tests

browser/base/content/test/browser_bug553455.js

@@ -591,6 +591,7 @@ function runNextTest() {
 };
 
 function test() {
+  requestLongerTimeout(2);
   waitForExplicitFinish();
 
   Services.prefs.setBoolPref("extensions.logging.enabled", true);