diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_485482.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_485482.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,37 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = ROOT + "browser_485482_sample.html";
+
+/**
+ * Bug 485482 - Make sure that we produce valid XPath expressions even for very
+ * weird HTML documents.
+ */
+add_task(function test_xpath_exp_for_strange_documents() {
+  // Load a page with weird tag names.
+  let tab = gBrowser.addTab(URL);
+  let browser = tab.linkedBrowser;
+  yield promiseBrowserLoaded(browser);
+
+  // Fill in some values.
+  let uniqueValue = Math.random();
+  yield setInputValue(browser, {selector: "input[type=text]", value: uniqueValue});
+  yield setInputChecked(browser, {selector: "input[type=checkbox]", checked: true});
+
+  // Duplicate the tab.
+  let tab2 = gBrowser.duplicateTab(tab);
+  let browser2 = tab2.linkedBrowser;
+  yield promiseTabRestored(tab2);
+
+  // Check that we generated valid XPath expressions to restore form values.
+  let text = yield getInputValue(browser2, {selector: "input[type=text]"});
+  is(text, uniqueValue, "generated XPath expression was valid");
+  let checkbox = yield getInputChecked(browser2, {selector: "input[type=checkbox]"});
+  ok(checkbox, "generated XPath expression was valid");
+
+  // Cleanup.
+  gBrowser.removeTab(tab2);
+  gBrowser.removeTab(tab);
+});