diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/ui/button/contract.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/ui/button/contract.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,62 @@
+/* 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';
+
+const { contract } = require('../../util/contract');
+const { isLocalURL } = require('../../url');
+const { isNil, isObject, isString } = require('../../lang/type');
+const { required, either, string, boolean, object } = require('../../deprecated/api-utils');
+const { merge } = require('../../util/object');
+const { freeze } = Object;
+
+function isIconSet(icons) {
+  return Object.keys(icons).
+    every(size => String(size >>> 0) === size && isLocalURL(icons[size]))
+}
+
+let iconSet = {
+  is: either(object, string),
+  map: v => isObject(v) ? freeze(merge({}, v)) : v,
+  ok: v => (isString(v) && isLocalURL(v)) || (isObject(v) && isIconSet(v)),
+  msg: 'The option "icon" must be a local URL or an object with ' +
+    'numeric keys / local URL values pair.'
+}
+
+let id = {
+  is: string,
+  ok: v => /^[a-z-_][a-z0-9-_]*$/i.test(v),
+  msg: 'The option "id" must be a valid alphanumeric id (hyphens and ' +
+        'underscores are allowed).'
+};
+
+let label = {
+  is: string,
+  ok: v => isNil(v) || v.trim().length > 0,
+  msg: 'The option "label" must be a non empty string'
+}
+
+let stateContract = contract({
+  label: label,
+  icon: iconSet,
+  disabled: boolean
+});
+
+exports.stateContract = stateContract;
+
+let buttonContract = contract(merge({}, stateContract.rules, {
+  id: required(id),
+  label: required(label),
+  icon: required(iconSet)
+}));
+
+exports.buttonContract = buttonContract;
+
+exports.toggleStateContract = contract(merge({
+  checked: boolean
+}, stateContract.rules));
+
+exports.toggleButtonContract = contract(merge({
+  checked: boolean
+}, buttonContract.rules));
+