Add a mojoPrivate API that exposes mojo to component apps/extensions.

extensions/test/data/mojo_private_unittest.js

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+'use strict';
+
+let mojoPrivate = require('mojoPrivate').binding;
+let test = require('test').binding;
+let unittestBindings = require('test_environment_specific_bindings');
+
+unittestBindings.exportTests([
+  function testDefine() {
+    mojoPrivate.define('testModule', [
+      'mojo/public/js/codec',
+    ], test.callbackPass(function(codec) {
+      test.assertEq('function', typeof codec.Message);
+    }));
+  },
+
+  function testDefineRegistersModule() {
+    mojoPrivate.define('testModule', ['dependency'],
+                       test.callbackPass(function(module) {
+      test.assertEq(12345, module.result);
+    }));
+    mojoPrivate.define('dependency', test.callbackPass(function() {
+      return {result: 12345};
+    }));
+  },
+
+  function testDefineModuleDoesNotExist() {
+    mojoPrivate.define('testModule', ['does not exist!'], test.fail);
+    test.succeed();
+  },
+], test.runTests, exports);