diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/stylesheet/style.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/stylesheet/style.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,81 @@
+/* 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 { Class } = require("../core/heritage");
+const { ns } = require("../core/namespace");
+const { URL } = require('../url');
+const events = require("../system/events");
+const { loadSheet, removeSheet, isTypeValid } = require("./utils");
+const { isString } = require("../lang/type");
+const { attachTo, detachFrom, getTargetWindow } = require("../content/mod");
+
+const { freeze, create } = Object;
+const LOCAL_URI_SCHEMES = ['resource', 'data'];
+
+function isLocalURL(item) {
+  try {
+    return LOCAL_URI_SCHEMES.indexOf(URL(item).scheme) > -1;
+  }
+  catch(e) {}
+
+  return false;
+}
+
+function Style({ source, uri, type }) {
+  source = source == null ? null : freeze([].concat(source));
+  uri = uri == null ? null : freeze([].concat(uri));
+  type = type == null ? "author" : type;
+
+  if (source && !source.every(isString))
+    throw new Error('Style.source must be a string or an array of strings.');
+
+  if (uri && !uri.every(isLocalURL))
+    throw new Error('Style.uri must be a local URL or an array of local URLs');
+
+  if (type && !isTypeValid(type))
+    throw new Error('Style.type must be "agent", "user" or "author"');
+
+  return freeze(create(Style.prototype, {
+    "source": { value: source, enumerable: true },
+    "uri": { value: uri, enumerable: true },
+    "type": { value: type, enumerable: true }
+  }));
+};
+
+exports.Style = Style;
+
+attachTo.define(Style, function (style, window) {
+  if (style.uri) {
+    for (let uri of style.uri)
+      loadSheet(window, uri, style.type);
+  }
+
+  if (style.source) {
+    let uri = "data:text/css;charset=utf-8,";
+
+    uri += encodeURIComponent(style.source.join(""));
+
+    loadSheet(window, uri, style.type);
+  }
+});
+
+detachFrom.define(Style, function (style, window) {
+  if (style.uri)
+    for (let uri of style.uri)
+      removeSheet(window, uri);
+
+  if (style.source) {
+    let uri = "data:text/css;charset=utf-8,";
+
+    uri += encodeURIComponent(style.source.join(""));
+
+    removeSheet(window, uri, style.type);
+  }
+});