diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/content_aboutAccounts.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/content_aboutAccounts.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,48 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file is loaded as a "content script" for browser_aboutAccounts tests
+"use strict";
+
+addEventListener("load", function load(event) {
+  if (event.target != content.document) {
+    return;
+  }
+//  content.document.removeEventListener("load", load, true);
+  sendAsyncMessage("test:document:load");
+}, true);
+
+addEventListener("DOMContentLoaded", function domContentLoaded(event) {
+  removeEventListener("DOMContentLoaded", domContentLoaded, true);
+  let iframe = content.document.getElementById("remote");
+  iframe.addEventListener("load", function iframeLoaded(event) {
+    if (iframe.contentWindow.location.href == "about:blank" ||
+        event.target != iframe) {
+      return;
+    }
+    iframe.removeEventListener("load", iframeLoaded, true);
+    sendAsyncMessage("test:iframe:load", {url: iframe.getAttribute("src")});
+  }, true);
+}, true);
+
+// Return the visibility state of a list of ids.
+addMessageListener("test:check-visibilities", function (message) {
+  let result = {};
+  for (let id of message.data.ids) {
+    let elt = content.document.getElementById(id);
+    if (elt) {
+      let displayStyle = content.window.getComputedStyle(elt).display;
+      if (displayStyle == 'none') {
+        result[id] = false;
+      } else if (displayStyle == 'block') {
+        result[id] = true;
+      } else {
+        result[id] = "strange: " + displayStyle; // tests should fail!
+      }
+    } else {
+      result[id] = "doesn't exist: " + id;
+    }
+  }
+  sendAsyncMessage("test:check-visibilities-response", result);
+});