Improves how to initialize polymer apps and fixes polymer build and linter to

pkg/polymer/test/event_path_test.dart

Index: pkg/polymer/test/event_path_test.dart
diff --git a/pkg/polymer/test/event_path_test.dart b/pkg/polymer/test/event_path_test.dart
index 33515027d11e6b73004ccdaede3cdc37c40781ea..f1e23eb0d8d8b3c94eb8aa38b76432e1df7b1f15 100644
--- a/pkg/polymer/test/event_path_test.dart
+++ b/pkg/polymer/test/event_path_test.dart
@@ -9,7 +9,28 @@ import 'package:polymer/polymer.dart';
 import 'package:unittest/html_config.dart';
 import 'package:unittest/unittest.dart';
 
-@initMethod _main() {
+@CustomTag("x-selector")
+class XSelector extends PolymerElement {
+  XSelector.created() : super.created();
+}
+
+@CustomTag("x-overlay")
+class XOverlay extends PolymerElement {
+  XOverlay.created() : super.created();
+}
+
+@CustomTag("x-menu")
+class XMenu extends PolymerElement {
+  XMenu.created() : super.created();
+}
+
+@CustomTag("x-menu-button")
+class XMenuButton extends PolymerElement {
+  XMenuButton.created() : super.created();
+}
+
+main() {
+  initPolymer();
   useHtmlConfiguration();
 
   setUp(() => Polymer.onReady);