Bug 1113391 - Followup to bug 923897 r=me

dom/apps/tests/addons/script2.js

@@ -0,0 +1,4 @@
+document.addEventListener("DOMContentLoaded", function() {
+  var head = document.getElementById("header2");
+  head.innerHTML = "Customized content";
+}, false);

dom/apps/tests/addons/style2.css

@@ -0,0 +1,3 @@
+#header2 {
+  color: blue;
+}