diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_581593.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_581593.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,46 @@
+/* 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/. */
+
+let stateBackup = ss.getBrowserState();
+
+function test() {
+  /** Test for bug 581593 **/
+  waitForExplicitFinish();
+  ignoreAllUncaughtExceptions();
+
+  let oldState = { windows: [{ tabs: [{ entries: [{ url: "example.com" }] }] }]};
+  let pageData = {
+    url: "about:sessionrestore",
+    formdata: { id: { "sessionData": "(" + JSON.stringify(oldState) + ")" } }
+  };
+  let state = { windows: [{ tabs: [{ entries: [pageData] }] }] };
+
+  // The form data will be restored before SSTabRestored, so we want to listen
+  // for that on the currently selected tab (it will be reused)
+  gBrowser.selectedTab.addEventListener("SSTabRestored", onSSTabRestored, true);
+
+  ss.setBrowserState(JSON.stringify(state));
+}
+
+function onSSTabRestored(aEvent) {
+  info("SSTabRestored event");
+  gBrowser.selectedTab.removeEventListener("SSTabRestored", onSSTabRestored, true);
+
+  // This is an ok way to check this because we will make sure that the text
+  // field is parsable.
+  let val = gBrowser.selectedBrowser.contentDocument.getElementById("sessionData").value;
+  try {
+    JSON.parse(val);
+    ok(true, "JSON.parse succeeded");
+  }
+  catch (e) {
+    ok(false, "JSON.parse failed");
+  }
+  cleanup();
+}
+
+function cleanup() {
+  ss.setBrowserState(stateBackup);
+  executeSoon(finish);
+}