Run pub tests against older versions of barback.

third_party/pkg/barback-0.13.0/lib/src/utils.dart

Index: third_party/pkg/barback-0.13.0/lib/src/utils.dart
diff --git a/pkg/barback/lib/src/utils.dart b/third_party/pkg/barback-0.13.0/lib/src/utils.dart
similarity index 93%
copy from pkg/barback/lib/src/utils.dart
copy to third_party/pkg/barback-0.13.0/lib/src/utils.dart
index d5a9fb62dd1130684c73390fd2904d7f7ccafbff..d2ce0495130b728187dd9e26d5247766e91a206f 100644
--- a/pkg/barback/lib/src/utils.dart
+++ b/third_party/pkg/barback-0.13.0/lib/src/utils.dart
@@ -308,20 +308,3 @@ Stream callbackStream(Stream callback()) {
       sync: true);
   return controller.stream;
 }
-
-/// Creates a single-subscription stream from a broadcast stream.
-///
-/// The returned stream will enqueue events from [broadcast] until a listener is
-/// attached, then pipe events to that listener.
-Stream broadcastToSingleSubscription(Stream broadcast) {
-  if (!broadcast.isBroadcast) return broadcast;
-
-  // TODO(nweiz): Implement this using a transformer when issues 18588 and 18586
-  // are fixed.
-  var subscription;
-  var controller = new StreamController(onCancel: () => subscription.cancel());
-  subscription = broadcast.listen(controller.add,
-      onError: controller.addError,
-      onDone: controller.close);
-  return controller.stream;
-}