Bring back initPolymer, allow boot.js only if using "polymer_experimental.html".

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 34 matching lines @@
 class XBaz extends PolymerElement {
   XBaz.created() : super.created();
   @observable int qux = 13;
 }
 
 @CustomTag('x-qux')
 class XQux extends XBaz {
   XQux.created() : super.created();
 }
 
-@initMethod
-main() {
+main() => initPolymer().run(() {
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);
 
   test('published properties', () {
     published(tag) => (new Element.tag(tag) as PolymerElement)
         .declaration.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']);
   });
-}
+});