fix libraries getter

pkg/dev_compiler/lib/js/legacy/dart_library.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.
 
 /* This file defines the module loader for the dart runtime.
 */
 var dart_library;
 if (!dart_library) {
 dart_library =
   typeof module != "undefined" && module.exports || {};
@@ skipping 119 matching lines @@
     stub() {
       return this._library;
     }
   }
   LibraryLoader.NOT_LOADED = 0;
   LibraryLoader.LOADING = 1;
   LibraryLoader.READY = 2;
 
   // Map from name to LibraryLoader
   let _libraries = new Map();
-  dart_library.libraries = function() { return libraries.keys(); };
+  dart_library.libraries = function() { return _libraries.keys(); };
   dart_library.debuggerLibraries = function() {
     var debuggerLibraries = [];
     _libraries.forEach(function (value, key, map) {
       debuggerLibraries.push(value.load());
     });
     debuggerLibraries.__proto__ = null;
     return debuggerLibraries;
   };
 
   // Invalidate a library and all things that depend on it
@@ skipping 111 matching lines @@
     } else {
       // If not a reload then store the initial html to reset it on reload.
       _originalBody = document.body.cloneNode(true);
     }
     library.main();
   }
   dart_library.start = start;
 
 })(dart_library);
 }