Update to polymer js version 0.4.1

pkg/observe/test/path_observer_test.dart

 // Copyright (c) 2013, 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.
 
 import 'dart:async';
 import 'package:observe/observe.dart';
 import 'package:unittest/unittest.dart';
 import 'package:observe/src/path_observer.dart'
     show getSegmentsOfPropertyPathForTesting,
          observerSentinelForTesting;
@@ skipping 54 matching lines @@
       expectPath('opt0', 'opt0', 1, [#opt0]);
       // Dart note: Modified to avoid a private Dart symbol:
       expectPath(r'$foo.$bar.baz_', r'$foo.$bar.baz_', 3,
           [#$foo, #$bar, #baz_]);
       // Dart note: this test is different because we treat ["baz"] always as a
       // indexing operation.
       expectPath('foo["baz"]', 'foo.baz', 2, [#foo, #baz]);
       expectPath('foo["b\\"az"]', 'foo["b\\"az"]', 2, [#foo, 'b"az']);
       expectPath("foo['b\\'az']", 'foo["b\'az"]', 2, [#foo, "b'az"]);
       expectPath([#a, #b], 'a.b', 2, [#a, #b]);
+      expectPath([], '', 0, []);
 
       expectPath('.', '<invalid path>', 0);
       expectPath(' . ', '<invalid path>', 0);
       expectPath('..', '<invalid path>', 0);
       expectPath('a[4', '<invalid path>', 0);
       expectPath('a.b.', '<invalid path>', 0);
       expectPath('a,b', '<invalid path>', 0);
       expectPath('a["foo]', '<invalid path>', 0);
       expectPath('[0x04]', '<invalid path>', 0);
       expectPath('[0foo]', '<invalid path>', 0);
@@ skipping 651 matching lines @@
   @observable var c;
 
   WatcherModel();
 }
 
 class Foo {
   var value;
   Foo(this.value);
   String toString() => 'Foo$value';
 }