Only pass an AssetId to isPrimary and declareOutputs.

pkg/smoke/lib/src/default_transformer.dart

 // Copyright (c) 2014, 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.
 
 /// Transformer that replaces the default mirror-based implementation of smoke,
 /// so that during deploy smoke doesn't include any dependency on dart:mirrors.
 library smoke.src.default_transformer;
 
 import 'dart:async';
 import 'package:barback/barback.dart';
 
 /// Replaces the default mirror-based implementation of smoke in
 /// `pacakge:smoke/implementation.dart`, so that during deploy smoke doesn't
 /// include any dependency on dart:mirrors.
 // TODO(sigmund): include tests that run this transformation automatically.
 class DefaultTransformer extends Transformer {
   DefaultTransformer.asPlugin();
 
   /// Only apply to `lib/src/implementation.dart`.
-  Future<bool> isPrimary(Asset input) => new Future.value(
-      input.id.package == 'smoke' &&
-      input.id.path == 'lib/src/implementation.dart');
+  // TODO(nweiz): This should just take an AssetId when barback <0.13.0 support
+  // is dropped.
+  Future<bool> isPrimary(idOrAsset) {
+    var id = idOrAsset is AssetId ? idOrAsset : idOrAsset.id;
+    return new Future.value(
+        id.package == 'smoke' && id.path == 'lib/src/implementation.dart');
+  }
 
   Future apply(Transform transform) {
     var id = transform.primaryInput.id;
     return transform.primaryInput.readAsString().then((code) {
       // Note: this rewrite is highly-coupled with how implementation.dart is
       // written. Make sure both are updated in sync.
       transform.addOutput(new Asset.fromString(id, code
           .replaceAll(new RegExp('new Reflective[^;]*;'),
               'throwNotConfiguredError();')
           .replaceAll("import 'package:smoke/mirrors.dart';", '')));
     });
   }
 }
 
 /** Transformer phases which should be applied to the smoke package. */
 List<List<Transformer>> get phasesForSmoke =>
     [[new DefaultTransformer.asPlugin()]];