Only pass an AssetId to isPrimary and declareOutputs.

pkg/barback/test/transformer/log.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.log;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:barback/src/utils.dart';
 
 import 'mock.dart';
 
 /// A transformer that logs given entries during its apply.
 class LogTransformer extends MockTransformer {
   /// The list of entries that it should log.
   ///
   /// Each entry has the log level followed by the message, like:
   ///
   ///     error: This is the error message.
   final List<String> _entries;
 
   LogTransformer(this._entries);
 
-  Future<bool> doIsPrimary(Asset asset) => new Future.value(true);
+  Future<bool> doIsPrimary(_) => new Future.value(true);
 
   Future doApply(Transform transform) {
     return newFuture(() {
       for (var entry in _entries) {
         var parts = entry.split(":");
         var logFn;
         switch (parts[0]) {
           case "error":   logFn = transform.logger.error; break;
           case "warning": logFn = transform.logger.warning; break;
           case "info":    logFn = transform.logger.info; break;
           case "fine":    logFn = transform.logger.fine; break;
         }
 
         logFn(parts[1].trim());
       }
     });
   }
 }