diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/stylesheet/utils.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/stylesheet/utils.js	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/. */
+
+"use strict";
+
+module.metadata =  {
+  "stability": "experimental"
+};
+
+const { Cc, Ci } = require("chrome");
+
+const io = Cc['@mozilla.org/network/io-service;1'].
+            getService(Ci.nsIIOService);
+
+const SHEET_TYPE = {
+  "agent": "AGENT_SHEET",
+  "user": "USER_SHEET",
+  "author": "AUTHOR_SHEET"
+};
+
+function getDOMWindowUtils(window) {
+  return window.QueryInterface(Ci.nsIInterfaceRequestor).
+                getInterface(Ci.nsIDOMWindowUtils);
+};
+
+/**
+ * Synchronously loads a style sheet from `uri` and adds it to the list of
+ * additional style sheets of the document.
+ * The sheets added takes effect immediately, and only on the document of the
+ * `window` given.
+ */
+function loadSheet(window, url, type) {
+  if (!(type && type in SHEET_TYPE))
+    type = "author";
+
+  type = SHEET_TYPE[type];
+
+  if (!(url instanceof Ci.nsIURI))
+    url = io.newURI(url, null, null);
+
+  let winUtils = getDOMWindowUtils(window);
+  try {
+    winUtils.loadSheet(url, winUtils[type]);
+  }
+  catch (e) {};
+};
+exports.loadSheet = loadSheet;
+
+/**
+ * Remove the document style sheet at `sheetURI` from the list of additional
+ * style sheets of the document.  The removal takes effect immediately.
+ */
+function removeSheet(window, url, type) {
+  if (!(type && type in SHEET_TYPE))
+    type = "author";
+
+  type = SHEET_TYPE[type];
+
+  if (!(url instanceof Ci.nsIURI))
+    url = io.newURI(url, null, null);
+
+  let winUtils = getDOMWindowUtils(window);
+
+  try {
+    winUtils.removeSheet(url, winUtils[type]);
+  }
+  catch (e) {};
+};
+exports.removeSheet = removeSheet;
+
+/**
+ * Returns `true` if the `type` given is valid, otherwise `false`.
+ * The values currently accepted are: "agent", "user" and "author".
+ */
+function isTypeValid(type) {
+  return type in SHEET_TYPE;
+}
+exports.isTypeValid = isTypeValid;