Run pub tests against older versions of barback.

third_party/pkg/barback-0.13.0/test/transformer/bad_log.dart

Index: third_party/pkg/barback-0.13.0/test/transformer/bad_log.dart
diff --git a/pkg/barback/test/transformer/bad_log.dart b/third_party/pkg/barback-0.13.0/test/transformer/bad_log.dart
similarity index 56%
copy from pkg/barback/test/transformer/bad_log.dart
copy to third_party/pkg/barback-0.13.0/test/transformer/bad_log.dart
index b84f105918ae833742f3c5076414d330545185ad..5d77b937ab0c71943db351dd9a08fba514b52cb1 100644
--- a/pkg/barback/test/transformer/bad_log.dart
+++ b/third_party/pkg/barback-0.13.0/test/transformer/bad_log.dart
@@ -4,7 +4,10 @@
 
 library barback.test.transformer.bad_log;
 
+import 'dart:async';
+
 import 'package:barback/barback.dart';
+import 'package:barback/src/utils.dart';
 
 import 'mock.dart';
 
@@ -16,15 +19,17 @@ class BadLogTransformer extends MockTransformer {
 
   BadLogTransformer(this.outputs);
 
-  bool doIsPrimary(AssetId id) => true;
+  Future<bool> doIsPrimary(AssetId id) => new Future.value(true);
 
-  void doApply(Transform transform) {
-    transform.logger.error("first error");
-    transform.logger.error("second error");
+  Future doApply(Transform transform) {
+    return newFuture(() {
+      transform.logger.error("first error");
+      transform.logger.error("second error");
 
-    for (var output in outputs) {
-      var id = new AssetId.parse(output);
-      transform.addOutput(new Asset.fromString(id, output));
-    }
+      for (var output in outputs) {
+        var id = new AssetId.parse(output);
+        transform.addOutput(new Asset.fromString(id, output));
+      }
+    });
   }
 }