Don't require Transformer methods to return Futures.

pkg/barback/test/transformer/catch_asset_not_found.dart

Index: pkg/barback/test/transformer/catch_asset_not_found.dart
diff --git a/pkg/barback/test/transformer/catch_asset_not_found.dart b/pkg/barback/test/transformer/catch_asset_not_found.dart
index ee5371dff1e07927feddcf3ab8c23ef850749a70..b43eeb753c2180c356643c85c0ee771bc3d35cc9 100644
--- a/pkg/barback/test/transformer/catch_asset_not_found.dart
+++ b/pkg/barback/test/transformer/catch_asset_not_found.dart
@@ -7,7 +7,6 @@ library barback.test.transformer.catch_asset_not_found;
 import 'dart:async';
 
 import 'package:barback/barback.dart';
-import 'package:barback/src/utils.dart';
 
 import 'mock.dart';
 
@@ -23,8 +22,7 @@ class CatchAssetNotFoundTransformer extends MockTransformer {
   CatchAssetNotFoundTransformer(this.extension, String input)
       : input = new AssetId.parse(input);
 
-  Future<bool> doIsPrimary(AssetId id) =>
-      new Future.value(id.extension == extension);
+  bool doIsPrimary(AssetId id) => id.extension == extension;
 
   Future doApply(Transform transform) {
     return transform.getInput(input).then((_) {