Update TodoMVC and other samples for polymer 0.10.0-pre.7

dart/samples/third_party/todomvc/test/markdone_shadow_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.
 
 library todomvc.test.markdone_shadow_test;
 
 // We don't use this import, but it signals to the test framework that this is
 // a web test.
 import 'dart:html';
 import 'markdone_test.dart' as markdone_test;
+import 'package:polymer/polymer.dart' show initMethod;
 
+@initMethod
 main() {
   // Make analyzer happy by using dart:html.
   document.querySelector('body');
   markdone_test.main();
 }