Check for null prototype in isJavaScriptSimpleObject

tests/html/postmessage_structured_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file
 
 library postmessage_js_test;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_individual_config.dart';
 import 'dart:html';
 import 'dart:collection';  // SplayTreeMap
 import 'dart:typed_data';
@@ skipping 60 matching lines @@
           if (data is String) return;    // Messages from unit test protocol.
           completed = true;
           subscription.cancel();
           expect(data, isMap);
           expect(data['eggs'], equals(3));
         },
         () => completed));
       injectSource(JS_CODE);
     });
 
+    test('js-to-dart--null-prototype-eventdata', () {
+      // Pass an object with a null prototype from JavaScript.
+      // It should be seen as a Dart Map.
+      final JS_CODE = """
+         // Call anonymous function to create a local scope.
+         (function() {
+            var o = Object.create(null);
+            o.eggs = 3;
+            var foo = new MessageEvent('stuff', {data: o});
+            window.dispatchEvent(foo);
+          })();
+        """;
+      var completed = false;
+      var subscription = null;
+      subscription = window.on['stuff'].listen(expectAsyncUntil(
+        (MessageEvent e) {
+          var data = e.data;
+          if (data is String) return;    // Messages from unit test protocol.
+          completed = true;
+          subscription.cancel();
+          expect(data, isMap);
+          expect(data['eggs'], equals(3));
+        },
+        () => completed));
+      injectSource(JS_CODE);
+    });
+
     test('dart-to-js-to-dart-postmessage', () {
       // Pass dictionaries between Dart and JavaScript.
 
       final JS_CODE = """
         window.addEventListener('message', handler);
         function handler(e) {
           var data = e.data;
           if (typeof data == 'string') return;
           if (data.recipient != 'JS') return;
           var response = {recipient: 'DART'};
@@ skipping 65 matching lines @@
         iframe.contentWindow.postMessage(new HashMap<String,num>(), '*');
       });
       iframe.src = 'about:blank';
       document.body.append(iframe);
 
       return future;
     });
   });
 
 }