diff -r 000000000000 -r 6474c204b198 toolkit/modules/PermissionsUtils.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/modules/PermissionsUtils.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,79 @@
+// 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/.
+
+this.EXPORTED_SYMBOLS = ["PermissionsUtils"];
+
+const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/Services.jsm");
+
+
+let gImportedPrefBranches = new Set();
+
+function importPrefBranch(aPrefBranch, aPermission, aAction) {
+  let list = Services.prefs.getChildList(aPrefBranch, {});
+
+  for (let pref of list) {
+    let hosts = "";
+    try {
+      hosts = Services.prefs.getCharPref(pref);
+    } catch (e) {}
+
+    if (!hosts)
+      continue;
+
+    hosts = hosts.split(",");
+
+    for (let host of hosts) {
+      try {
+        let uri = Services.io.newURI("http://" + host, null, null);
+        Services.perms.add(uri, aPermission, aAction);
+      } catch (e) {}
+    }
+
+    Services.prefs.setCharPref(pref, "");
+  }
+}
+
+
+this.PermissionsUtils = {
+  /**
+   * Import permissions from perferences to the Permissions Manager. After being
+   * imported, all processed permissions will be set to an empty string.
+   * Perferences are only processed once during the application's
+   * lifetime - it's safe to call this multiple times without worrying about
+   * doing unnecessary work, as the preferences branch will only be processed
+   * the first time.
+   *
+   * @param aPrefBranch  Preferences branch to import from. The preferences
+   *                     under this branch can specify whitelist (ALLOW_ACTION)
+   *                     or blacklist (DENY_ACTION) additions using perference
+   *                     names of the form:
+   *                     * <BRANCH>.whitelist.add.<ID>
+   *                     * <BRANCH>.blacklist.add.<ID>
+   *                     Where <ID> can be any valid preference name.
+   *                     The value is expected to be a comma separated list of
+   *                     host named. eg:
+   *                     * something.example.com
+   *                     * foo.exmaple.com,bar.example.com
+   *
+   * @param aPermission Permission name to be passsed to the Permissions
+   *                    Manager.
+   */
+  importFromPrefs: function(aPrefBranch, aPermission) {
+    if (!aPrefBranch.endsWith("."))
+      aPrefBranch += ".";
+
+    // Ensure we only import this pref branch once.
+    if (gImportedPrefBranches.has(aPrefBranch))
+     return;
+
+    importPrefBranch(aPrefBranch + "whitelist.add", aPermission,
+                     Services.perms.ALLOW_ACTION);
+    importPrefBranch(aPrefBranch + "blacklist.add", aPermission,
+                     Services.perms.DENY_ACTION);
+
+    gImportedPrefBranches.add(aPrefBranch);
+  }
+};