Don't require Transformer methods to return Futures.

pkg/barback/test/transformer/lazy_bad.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library barback.test.transformer.lazy_bad;
 
-import 'dart:async';
-
 import 'package:barback/barback.dart';
-import 'package:barback/src/utils.dart';
 
 import 'mock.dart';
 
 /// A lazy transformer that throws an exception after [declareOutputs].
 class LazyBadTransformer extends MockTransformer implements LazyTransformer {
   /// The error [this] throws.
   static const ERROR = "I am a bad transformer!";
 
   /// The asset name that [this] should output.
   final String output;
 
   LazyBadTransformer(this.output);
 
-  Future<bool> doIsPrimary(_) => new Future.value(true);
+  bool doIsPrimary(AssetId id) => true;
 
-  Future doApply(Transform transform) {
-    return newFuture(() {
-      var id = new AssetId.parse(output);
-      transform.addOutput(new Asset.fromString(id, output));
-    });
+  void doApply(Transform transform) {
+    var id = new AssetId.parse(output);
+    transform.addOutput(new Asset.fromString(id, output));
   }
 
-  Future declareOutputs(DeclaringTransform transform) {
-    return newFuture(() {
-      var id = new AssetId.parse(output);
-      transform.declareOutput(id);
-      throw ERROR;
-    });
+  void declareOutputs(DeclaringTransform transform) {
+    var id = new AssetId.parse(output);
+    transform.declareOutput(id);
+    throw ERROR;
   }
 }