Update comment to mention Blink bug

tests/html/mutationobserver_test.dart

 // Copyright (c) 2011, 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 mutationobserver_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:html';
 
-// MutationObservers sometimes do not fire if the node being observed is GCed
+// Due to https://code.google.com/p/chromium/issues/detail?id=329103
+// mutationObservers sometimes do not fire if the node being observed is GCed
 // so we keep around references to all nodes we have created mutation
-// observers for. As a side note, this behavior only manifests in content_shell
-// and not chrome and the behavior goes away in content_shell if the flag
-// -js-flags="--gc_global" is passed to content_shell. Note: the gc behavior
-// only has been detected when running dart2js but could equally reasonably
-// impact the dartvm as well unless it is specified that mutation events must
-// be delivered even if the object the events are for has already been GCed.
+// observers for.
 var keepAlive = [];
 
 /**
  * Test suite for Mutation Observers. This is just a small set of sanity
  * checks, not a complete test suite.
  */
 main() {
   useHtmlIndividualConfiguration();
 
   group('supported', () {
@@ skipping 79 matching lines @@
         var mutationObserver = new MutationObserver(
             mutationCallback(2, orderedEquals([div1, div2])));
         mutationObserver.observe(container, childList: true, subtree: true);
 
         container.append(div1);
         div1.append(div2);
       }, expectation);
     });
   });
 }