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

tests/html/custom/created_callback_test.dart

Index: tests/html/custom/created_callback_test.dart
diff --git a/tests/html/custom/created_callback_test.dart b/tests/html/custom/created_callback_test.dart
index 00848c46dca67ed8cfff93bb41949d36226250a8..ebd3fba3c8c133acd7f1e307ef37cdc01d01cf49 100644
--- a/tests/html/custom/created_callback_test.dart
+++ b/tests/html/custom/created_callback_test.dart
@@ -54,18 +54,6 @@ class C 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();