diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_662812.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_662812.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,36 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  waitForExplicitFinish();
+
+  window.addEventListener("SSWindowStateBusy", function onBusy() {
+    window.removeEventListener("SSWindowStateBusy", onBusy, false);
+
+    let state = JSON.parse(ss.getWindowState(window));
+    ok(state.windows[0].busy, "window is busy");
+
+    window.addEventListener("SSWindowStateReady", function onReady() {
+      window.removeEventListener("SSWindowStateReady", onReady, false);
+
+      let state = JSON.parse(ss.getWindowState(window));
+      ok(!state.windows[0].busy, "window is not busy");
+
+      executeSoon(() => {
+        gBrowser.removeTab(gBrowser.tabs[1]);
+        finish();
+      });
+    }, false);
+  }, false);
+
+  // create a new tab
+  let tab = gBrowser.addTab("about:mozilla");
+  let browser = tab.linkedBrowser;
+
+  // close and restore it
+  browser.addEventListener("load", function onLoad() {
+    browser.removeEventListener("load", onLoad, true);
+    gBrowser.removeTab(tab);
+    ss.undoCloseTab(window, 0);
+  }, true);
+}