diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_attributes.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_attributes.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,72 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function test() {
+  TestRunner.run();
+}
+
+/**
+ * This test makes sure that we correctly preserve tab attributes when storing
+ * and restoring tabs. It also ensures that we skip special attributes like
+ * 'image' and 'pending' that need to be handled differently or internally.
+ */
+
+const PREF = "browser.sessionstore.restore_on_demand";
+
+function runTests() {
+  Services.prefs.setBoolPref(PREF, true)
+  registerCleanupFunction(() => Services.prefs.clearUserPref(PREF));
+
+  // Add a new tab with a nice icon.
+  let tab = gBrowser.addTab("about:robots");
+  yield whenBrowserLoaded(tab.linkedBrowser);
+
+  // Check that the tab has an 'image' attribute.
+  ok(tab.hasAttribute("image"), "tab.image exists");
+
+  // Make sure we do not persist 'image' attributes.
+  ss.persistTabAttribute("image");
+  let {attributes} = JSON.parse(ss.getTabState(tab));
+  ok(!("image" in attributes), "'image' attribute not saved");
+  ok(!("custom" in attributes), "'custom' attribute not saved");
+
+  // Test persisting a custom attribute.
+  tab.setAttribute("custom", "foobar");
+  ss.persistTabAttribute("custom");
+
+  let {attributes} = JSON.parse(ss.getTabState(tab));
+  is(attributes.custom, "foobar", "'custom' attribute is correct");
+
+  // Make sure we're backwards compatible and restore old 'image' attributes.
+  let state = {
+    entries: [{url: "about:mozilla"}],
+    attributes: {custom: "foobaz", image: gBrowser.getIcon(tab)}
+  };
+
+  // Prepare a pending tab waiting to be restored.
+  whenTabRestoring(tab);
+  yield ss.setTabState(tab, JSON.stringify(state));
+
+  ok(tab.hasAttribute("pending"), "tab is pending");
+  is(gBrowser.getIcon(tab), state.attributes.image, "tab has correct icon");
+
+  // Let the pending tab load.
+  gBrowser.selectedTab = tab;
+  yield whenTabRestored(tab);
+
+  // Ensure no 'image' or 'pending' attributes are stored.
+  let {attributes} = JSON.parse(ss.getTabState(tab));
+  ok(!("image" in attributes), "'image' attribute not saved");
+  ok(!("pending" in attributes), "'pending' attribute not saved");
+  is(attributes.custom, "foobaz", "'custom' attribute is correct");
+
+  // Clean up.
+  gBrowser.removeTab(tab);
+}
+
+function whenTabRestoring(tab) {
+  tab.addEventListener("SSTabRestoring", function onRestoring() {
+    tab.removeEventListener("SSTabRestoring", onRestoring);
+    executeSoon(next);
+  });
+}