Fixing Node.clone not returning upgraded custom elements.

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 2238df6e2d67feb90e4ab107f06574d481984fe5..932f760072672b3fa415342c41cac7e399a07c1f 100644
--- a/tests/html/custom/constructor_calls_created_synchronously_test.dart
+++ b/tests/html/custom/constructor_calls_created_synchronously_test.dart
@@ -27,11 +27,28 @@ main() {
   // Adapted from Blink's
   // fast/dom/custom/constructor-calls-created-synchronously test.
 
-  setUp(loadPolyfills);
+  var registered = false;
+  setUp(() {
+    return loadPolyfills().then((_) {
+      if (!registered) {
+        registered = true;
+        document.register(A.tag, A);
+      }
+    });
+  });
 
   test('createdCallback', () {
-    document.register(A.tag, A);
     var x = new A();
     expect(A.ncallbacks, 1);
   });
+
+  test('clone node', () {
+    A.ncallbacks = 0;
+
+    var a = new A();
+    expect(A.ncallbacks, 1);
+    var b = a.clone(false);
+    expect(A.ncallbacks, 2);
+    expect(b is A, isTrue);
+  });
 }