fixes #221, initial sync*, async, async* implementation

lib/runtime/dart_runtime.js

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 dart_library.library('dart_runtime/dart', null, /* Imports */[
   'dart_runtime/_classes',
   'dart_runtime/_errors',
+  'dart_runtime/_generators',
   'dart_runtime/_operations',
   'dart_runtime/_rtti',
   'dart_runtime/_types',
 ], /* Lazy Imports */[
   'dart/_js_helper'
-], function(exports, classes, errors, operations, rtti, types, _js_helper) {
+], function(exports, classes, errors, generators, operations, rtti, types,
+    _js_helper) {
   'use strict';
 
   function _export(value) {
     if (value) return value;
     console.log("Re-exporting null field: " + name);
     throw "Bad export";
   }
 
   function exportFrom(value, names) {
     for (let name of names) {
@@ skipping 21 matching lines @@
     'defineExtensionNames',
     'defineExtensionMembers',
     'generic',
     'implements',
     'list',
     'metadata',
     'mixin',
     'registerExtension',
     'setBaseClass',
     'setSignature',
-    'virtualField',
-  ])
+    'virtualField'
+  ]);
+
+  exportFrom(generators, [
+    'syncStar',
+    'async',
+    'asyncStar'
+  ]);
 
   // From dart_utils
   exportFrom(dart_utils, ['copyProperties', 'instantiate']);
   // Renames
   exports.defineLazyClass = _export(dart_utils.defineLazy);
   exports.defineLazyProperties = _export(dart_utils.defineLazy);
   exports.defineLazyClassGeneric = _export(dart_utils.defineLazyProperty);
 
   // From operations
   exportFrom(operations, [
@@ skipping 33 matching lines @@
   ]);
 
   // From rtti
   exportFrom(rtti, [
     'fn',
     'realRuntimeType',
     'runtimeType',
   ]);
 
 });