Revert "Revert "Dart2js support for custom element lifecycle events""

tests/html/custom/constructor_calls_created_synchronously_test.dart

Index: tests/html/custom/constructor_calls_created_synchronously_test.dart
diff --git a/tests/html/custom/constructor_calls_created_synchronously_test.dart b/tests/html/custom/constructor_calls_created_synchronously_test.dart
index f383a7aa51d3024384e7c12755b1d9b58410d1ed..edd689ad8bd75a69cf313898491b2f47b5df1b44 100644
--- a/tests/html/custom/constructor_calls_created_synchronously_test.dart
+++ b/tests/html/custom/constructor_calls_created_synchronously_test.dart
@@ -6,6 +6,7 @@ library constructor_calls_created_synchronously_test;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import 'dart:html';
+import '../utils.dart';
 
 class A extends HtmlElement {
   static final tag = 'x-a';
@@ -18,18 +19,6 @@ class A extends HtmlElement {
   }
 }
 
-loadPolyfills() {
-  if (!document.supportsRegister) {
-    // Cache blocker is a workaround for:
-    // https://code.google.com/p/dart/issues/detail?id=11834
-    var cacheBlocker = new DateTime.now().millisecondsSinceEpoch;
-    return HttpRequest.getString('/root_dart/pkg/custom_element/lib/'
-      'custom-elements.debug.js?cacheBlock=$cacheBlocker').then((code) {
-      document.head.children.add(new ScriptElement()..text = code);
-    });
-  }
-}
-
 main() {
   useHtmlConfiguration();