[polymer] interop with polymer-element and polymer.js

pkg/polymer/test/publish_attributes_test.dart

Index: pkg/polymer/test/publish_attributes_test.dart
diff --git a/pkg/polymer/test/publish_attributes_test.dart b/pkg/polymer/test/publish_attributes_test.dart
index 6ff61a89662f493f5967ad0ff8a015b9d9dd2790..33966e744f404df4c9f458f673fc896eafc6c84d 100644
--- a/pkg/polymer/test/publish_attributes_test.dart
+++ b/pkg/polymer/test/publish_attributes_test.dart
@@ -59,8 +59,8 @@ main() {
   setUp(() => Polymer.onReady);
 
   test('published properties', () {
-    published(tag) => (querySelector('polymer-element[name=$tag]')
-        as PolymerDeclaration).publishedProperties;
+    published(tag) => (new Element.tag(tag) as PolymerElement)
+        .declaration.publishedProperties;
 
     expect(published('x-foo'), ['Foo', 'baz']);
     expect(published('x-bar'), ['Foo', 'baz', 'Bar']);