update elements and fix some bugs

test/paper_radio_button_basic_test.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.
 @TestOn('browser')
 library polymer_elements.test.paper_radio_button_basic_test;
 
 import 'dart:async';
 import 'package:test/test.dart';
 import 'package:web_components/web_components.dart';
 import 'package:polymer_elements/paper_radio_button.dart';
@@ skipping 52 matching lines @@
       r1 = fixture('NoLabel');
       r2 = fixture('WithLabel');
     });
 
     test('has aria role "radio"', () {
       expect(r1.attributes['role'], equals('radio'));
       expect(r2.attributes['role'], equals('radio'));
     });
 
     test('button with no label has no aria label', () {
-      expect(r1.attributes['aria-label'], isEmpty);
-    });
-
-    test('button with a label sets an aria label', () {
-      expect(r2.attributes['aria-label'], equals("Batman"));
+      expect(r1.attributes['aria-label'], isNull);
     });
 
     test('button respects the user set aria-label', () {
       var c = fixture('AriaLabel');
       expect(c.attributes['aria-label'], equals("Batman"));
     });
 
     // TODO(jakemac): Investigate these.
     // a11ySuite('NoLabel');
     // a11ySuite('WithLabel');
     // a11ySuite('AriaLabel');
   });
 }