Allow null assignments if there is a corresponding marker.

tests/html/input_element_test.dart

 library input_element_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 
 void check(InputElement element, String type, [bool supported = true]) {
   expect(element is InputElement, true);
   if (supported) {
     expect(element.type, type);
   } else {
@@ skipping 159 matching lines @@
     });
 
     test('reset', () {
       check(new ResetButtonInputElement(), 'reset');
     });
 
     test('button', () {
       check(new ButtonInputElement(), 'button');
     });
   });
+
+  group('attributes', () {
+    test('value = null', () {

[podivilov1, 2013/04/26 08:14:05]

test name might be confusing, valueSetNull maybe?

[Anton Muhin, 2013/04/26 08:47:53]

Done.

+      final e = new TextInputElement();
+      e.value = null;
+      expect(e.value, '');
+    });
+  });
 }