diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_dying_cache.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_dying_cache.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,80 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  TestRunner.run();
+}
+
+/**
+ * This test ensures that after closing a window we keep its state data around
+ * as long as something keeps a reference to it. It should only be possible to
+ * read data after closing - writing should fail.
+ */
+
+function runTests() {
+  // Open a new window.
+  let win = OpenBrowserWindow();
+  yield whenDelayedStartupFinished(win, next);
+
+  // Load some URL in the current tab.
+  let flags = Ci.nsIWebNavigation.LOAD_FLAGS_REPLACE_HISTORY;
+  win.gBrowser.selectedBrowser.loadURIWithFlags("about:robots", flags);
+  yield whenBrowserLoaded(win.gBrowser.selectedBrowser);
+
+  // Open a second tab and close the first one.
+  let tab = win.gBrowser.addTab("about:mozilla");
+  yield whenBrowserLoaded(tab.linkedBrowser);
+  SyncHandlers.get(tab.linkedBrowser).flush();
+  win.gBrowser.removeTab(win.gBrowser.tabs[0]);
+
+  // Make sure our window is still tracked by sessionstore
+  // and the window state is as expected.
+  ok("__SSi" in win, "window is being tracked by sessionstore");
+  ss.setWindowValue(win, "foo", "bar");
+  checkWindowState(win);
+
+  let state = ss.getWindowState(win);
+  let closedTabData = ss.getClosedTabData(win);
+
+  // Close our window and wait a tick.
+  whenWindowClosed(win);
+  yield win.close();
+
+  // SessionStore should no longer track our window
+  // but it should still report the same state.
+  ok(!("__SSi" in win), "sessionstore does no longer track our window");
+  checkWindowState(win);
+
+  // Make sure we're not allowed to modify state data.
+  ok(shouldThrow(() => ss.setWindowState(win, {})),
+     "we're not allowed to modify state data anymore");
+  ok(shouldThrow(() => ss.setWindowValue(win, "foo", "baz")),
+     "we're not allowed to modify state data anymore");
+}
+
+function checkWindowState(window) {
+  let {windows: [{tabs}]} = JSON.parse(ss.getWindowState(window));
+  is(tabs.length, 1, "the window has a single tab");
+  is(tabs[0].entries[0].url, "about:mozilla", "the tab is about:mozilla");
+
+  is(ss.getClosedTabCount(window), 1, "the window has one closed tab");
+  let [{state: {entries: [{url}]}}] = JSON.parse(ss.getClosedTabData(window));
+  is(url, "about:robots", "the closed tab is about:robots");
+
+  is(ss.getWindowValue(window, "foo"), "bar", "correct extData value");
+}
+
+function shouldThrow(f) {
+  try {
+    f();
+  } catch (e) {
+    return true;
+  }
+}
+
+function whenWindowClosed(window) {
+  window.addEventListener("SSWindowClosing", function onClosing() {
+    window.removeEventListener("SSWindowClosing", onClosing);
+    executeSoon(next);
+  });
+}