Making Indexed DB's cursor stream not auto-advance if no subscribers

sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart

 library dart.dom.indexed_db;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:_js_helper' show Creates, Returns, JSName, Null;
 import 'dart:_foreign_helper' show JS;
 // 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.
@@ skipping 996 matching lines @@
       //TODO: Report stacktrace once issue 4061 is resolved.
       controller.signalError(e);
     });
 
     request.onSuccess.listen((e) {
       Cursor cursor = request.result;
       if (cursor == null) {
         controller.close();
       } else {
         controller.add(cursor);
-        if (autoAdvance == true) {
+        if (autoAdvance == true && controller.hasSubscribers) {

[sra1, 2013/03/08 00:51:33]

is "== true" needed?

[blois, 2013/03/08 01:35:47]

When is a bool not really a bool? When it's null! (the param is optional, I
think this is a dumb language feature).

           cursor.next();
         }
       }
     });
     return controller.stream;
   }
 }
 // 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.
@@ skipping 210 matching lines @@
 }
 // 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.
 
 
 @DocsEditable
 @DomName('IDBAny')
 class _IDBAny native "*IDBAny" {
 }