diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/src/Utils.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/src/Utils.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,55 @@
+/* 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/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["Utils"];
+
+const Cu = Components.utils;
+
+Cu.import("resource://gre/modules/Services.jsm", this);
+
+this.Utils = Object.freeze({
+  makeURI: function (url) {
+    return Services.io.newURI(url, null, null);
+  },
+
+  /**
+   * Returns true if the |url| passed in is part of the given root |domain|.
+   * For example, if |url| is "www.mozilla.org", and we pass in |domain| as
+   * "mozilla.org", this will return true. It would return false the other way
+   * around.
+   */
+  hasRootDomain: function (url, domain) {
+    let host;
+
+    try {
+      host = this.makeURI(url).host;
+    } catch (e) {
+      // The given URL probably doesn't have a host.
+      return false;
+    }
+
+    let index = host.indexOf(domain);
+    if (index == -1)
+      return false;
+
+    if (host == domain)
+      return true;
+
+    let prevChar = host[index - 1];
+    return (index == (host.length - domain.length)) &&
+           (prevChar == "." || prevChar == "/");
+  },
+
+  shallowCopy: function (obj) {
+    let retval = {};
+
+    for (let key of Object.keys(obj)) {
+      retval[key] = obj[key];
+    }
+
+    return retval;
+  }
+});