Run pub tests against older versions of barback.

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

Index: third_party/pkg/barback-0.13.0/test/transformer/bad.dart
diff --git a/pkg/barback/test/transformer/bad.dart b/third_party/pkg/barback-0.13.0/test/transformer/bad.dart
similarity index 60%
copy from pkg/barback/test/transformer/bad.dart
copy to third_party/pkg/barback-0.13.0/test/transformer/bad.dart
index 0cc3496d059649e3487d64475a9f07649df9855f..a1e99cdc32331449f71181bfbd3ae3eabde9082b 100644
--- a/pkg/barback/test/transformer/bad.dart
+++ b/third_party/pkg/barback-0.13.0/test/transformer/bad.dart
@@ -4,7 +4,10 @@
 
 library barback.test.transformer.bad;
 
+import 'dart:async';
+
 import 'package:barback/barback.dart';
+import 'package:barback/src/utils.dart';
 
 import 'mock.dart';
 
@@ -19,16 +22,18 @@ class BadTransformer extends MockTransformer {
 
   BadTransformer(this.outputs);
 
-  bool doIsPrimary(AssetId id) => true;
+  Future<bool> doIsPrimary(AssetId id) => new Future.value(true);
 
-  void doApply(Transform transform) {
-    // Create the outputs first.
-    for (var output in outputs) {
-      var id = new AssetId.parse(output);
-      transform.addOutput(new Asset.fromString(id, output));
-    }
+  Future doApply(Transform transform) {
+    return newFuture(() {
+      // Create the outputs first.
+      for (var output in outputs) {
+        var id = new AssetId.parse(output);
+        transform.addOutput(new Asset.fromString(id, output));
+      }
 
-    // Then fail.
-    throw ERROR;
+      // Then fail.
+      throw ERROR;
+    });
   }
 }