fix todomvc tests

tools/dom/src/dart2js_CustomElementSupport.dart

Index: tools/dom/src/dart2js_CustomElementSupport.dart
diff --git a/tools/dom/src/dart2js_CustomElementSupport.dart b/tools/dom/src/dart2js_CustomElementSupport.dart
index 67cc05b34ff115f36e244169de4f218881d337b2..0f941fd981ec67676f798cc83f2fd756ecb0ed45 100644
--- a/tools/dom/src/dart2js_CustomElementSupport.dart
+++ b/tools/dom/src/dart2js_CustomElementSupport.dart
@@ -4,8 +4,10 @@
 
 part of dart.dom.html;
 
-_callConstructor(constructor) {
+_callConstructor(constructor, interceptor) {
   return (receiver) {
+    setNativeSubclassDispatchRecord(receiver, interceptor);
+
     return JS('', '#(#)', constructor, receiver);
   };
 }
@@ -62,6 +64,8 @@ void _registerCustomElement(context, document, String tag, Type type,
     throw new ArgumentError(type);
   }
 
+  var interceptor = JS('=Object', '#.prototype', interceptorClass);
+
   var constructor = findConstructorForNativeSubclassType(type, 'created');
   if (constructor == null) {
     throw new ArgumentError("$type has no constructor called 'created'");
@@ -94,7 +98,7 @@ void _registerCustomElement(context, document, String tag, Type type,
 
   JS('void', '#.createdCallback = #', properties,
       JS('=Object', '{value: #}',
-          _makeCallbackMethod(_callConstructor(constructor))));
+          _makeCallbackMethod(_callConstructor(constructor, interceptor))));
   JS('void', '#.enteredViewCallback = #', properties,
       JS('=Object', '{value: #}', _makeCallbackMethod(_callEnteredView)));
   JS('void', '#.leftViewCallback = #', properties,
@@ -111,8 +115,6 @@ void _registerCustomElement(context, document, String tag, Type type,
   var baseProto = JS('=Object', '#.prototype', baseConstructor);
   var proto = JS('=Object', 'Object.create(#, #)', baseProto, properties);
 
-  var interceptor = JS('=Object', '#.prototype', interceptorClass);
-
   setNativeSubclassDispatchRecord(proto, interceptor);
 
   var options = JS('=Object', '{prototype: #}', proto);