diff -r 000000000000 -r 6474c204b198 browser/devtools/debugger/test/addon-source/browser_dbg_addon3/lib/main.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/debugger/test/addon-source/browser_dbg_addon3/lib/main.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,13 @@
+var { Cc, Ci } = require("chrome");
+var { once } = require("sdk/system/events");
+
+var observerService = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);
+var observer = {
+  observe: function () {
+    debugger;
+  }
+};
+
+once("sdk:loader:destroy", () => observerService.removeObserver(observer, "debuggerAttached"));
+
+observerService.addObserver(observer, "debuggerAttached", false);