fixes #168, dart:js implementation with a test

lib/src/dependency_graph.dart

 // 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.
 
 /// Tracks the shape of the import/export graph and dependencies between files.
 library dev_compiler.src.dependency_graph;
 
 import 'dart:collection' show HashSet, HashMap;
 
 import 'package:analyzer/analyzer.dart' show parseDirectives;
@@ skipping 516 matching lines @@
   'dart._js_embedded_names',
   'dart._js_helper',
   'dart.isolate',
   'dart.typed_data',
   'dart._native_typed_data',
   'dart._isolate_helper',
   'dart._js_primitives',
   'dart.convert',
   'dart.mirrors',
   'dart._js_mirrors',
+  'dart.js'
   // _foreign_helper is not included, as it only defines the JS builtin that
   // the compiler handles at compile time.
 ];
 
 /// Runtime files added to applications when running in server mode.
 final runtimeFilesForServerMode = new List<String>.from(defaultRuntimeFiles)
   ..addAll(const ['messages_widget.js', 'messages.css']);
 
 final _log = new Logger('dev_compiler.dependency_graph');