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

sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart

Index: sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
diff --git a/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart b/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
index 9c3b3775fff5c5334be291e023b94f41b418b0ba..bcd55fdaf6f5ef3fad2b3d3dfe626ec6403eeee6 100644
--- a/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
+++ b/sdk/lib/indexed_db/dart2js/indexed_db_dart2js.dart
@@ -1014,7 +1014,7 @@ class ObjectStore native "*IDBObjectStore" {
         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();
         }
       }