diff -r 000000000000 -r 6474c204b198 js/xpconnect/tests/browser/browser_dead_object.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/xpconnect/tests/browser/browser_dead_object.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,24 @@
+/* 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/. */
+
+// For bug 773980, test that Components.utils.isDeadWrapper works as expected.
+function test() {
+  waitForExplicitFinish();
+
+  let tab = gBrowser.addTab("http://example.com");
+  let tabBrowser = tab.linkedBrowser;
+
+  tabBrowser.addEventListener("load", function loadListener(aEvent) {
+    tabBrowser.removeEventListener("load", loadListener, true);
+
+    let contentWindow = tab.linkedBrowser.contentWindow;
+    gBrowser.removeTab(tab);
+
+    SimpleTest.executeSoon(function() {
+      ok(Components.utils.isDeadWrapper(contentWindow),
+         'Window should be dead.');
+      finish();
+    });
+  }, true);
+}