[polymer.dart] fix *Changed observers inheriting

pkg/polymer/test/publish_attributes_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:html';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'package:polymer/polymer.dart';
 
 // Dart note: unlike JS, you can't publish something that doesn't
@@ skipping 19 matching lines @@
   XZot.created() : super.created();
 
   @published int zot = 3;
 }
 
 @CustomTag('x-squid')
 class XSquid extends XZot {
   XSquid.created() : super.created();
 
   @published int baz = 13;
-  @published int zot = 5;
+  @published int zot = 3;
   @published int squid = 7;
 }
 
+// Test inherited "attriubtes"
+class XBaz extends PolymerElement {
+  XBaz.created() : super.created();
+  @observable int qux = 13;
+}
+
+@CustomTag('x-qux')
+class XQux extends XBaz {
+  XQux.created() : super.created();
+}
+
 main() {
   initPolymer();
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   test('published properties', () {
     published(tag) => (query('polymer-element[name=$tag]')
         as PolymerDeclaration).publishedProperties;
 
     expect(published('x-foo'), [#Foo, #baz]);
     expect(published('x-bar'), [#Foo, #baz, #Bar]);
     expect(published('x-zot'), [#Foo, #baz, #Bar, #zot]);
     expect(published('x-squid'), [#Foo, #baz, #Bar, #zot, #squid]);
+    expect(published('x-qux'), [#qux]);
   });
 }