Support declaring and lazy transformers in pub.

sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart

Index: sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart b/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
index f1844daa401d9cc6e96df2bd058d388c6175a9d7..2d5d8cb23625855e7ade9a90e89e67da094810eb 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/load_transformers.dart
@@ -8,15 +8,13 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:isolate';
 
-import 'package:barback/barback.dart';
-
 import '../../../asset/dart/serialize.dart';
 import '../barback.dart';
 import '../dart.dart' as dart;
 import '../log.dart' as log;
 import '../utils.dart';
 import 'asset_environment.dart';
-import 'excluding_transformer.dart';
+import 'foreign_transformer.dart';
 import 'barback_server.dart';
 
 /// Load and return all transformers and groups from the library identified by
@@ -51,7 +49,7 @@ Future<Set> loadTransformers(AssetEnvironment environment,
         'configuration': JSON.encode(id.configuration)
       }).then((transformers) {
         transformers = transformers.map(
-            (transformer) => _deserializeTransformerOrGroup(transformer, id))
+            (transformer) => deserializeTransformerOrGroup(transformer, id))
             .toSet();
         log.fine("Transformers from $assetId: $transformers");
         return transformers;
@@ -73,63 +71,3 @@ Future<Set> loadTransformers(AssetEnvironment environment,
     });
   });
 }
-
-/// A wrapper for a transformer that's in a different isolate.
-class _ForeignTransformer extends Transformer {
-  /// The port with which we communicate with the child isolate.
-  ///
-  /// This port and all messages sent across it are specific to this
-  /// transformer.
-  final SendPort _port;
-
-  /// The result of calling [toString] on the transformer in the isolate.
-  final String _toString;
-
-  _ForeignTransformer(Map map)
-      : _port = map['port'],
-        _toString = map['toString'];
-
-  Future<bool> isPrimary(AssetId id) {
-    return call(_port, {
-      'type': 'isPrimary',
-      'id': serializeId(id)
-    });
-  }
-
-  Future apply(Transform transform) {
-    return call(_port, {
-      'type': 'apply',
-      'transform': serializeTransform(transform)
-    });
-  }
-
-  String toString() => _toString;
-}
-
-/// A wrapper for a transformer group that's in a different isolate.
-class _ForeignGroup implements TransformerGroup {
-  final Iterable<Iterable> phases;
-
-  /// The result of calling [toString] on the transformer group in the isolate.
-  final String _toString;
-
-  _ForeignGroup(TransformerId id, Map map)
-      : phases = map['phases'].map((phase) {
-          return phase.map((transformer) => _deserializeTransformerOrGroup(
-              transformer, id)).toList();
-        }).toList(),
-        _toString = map['toString'];
-
-  String toString() => _toString;
-}
-
-/// Converts a serializable map into a [Transformer] or a [TransformerGroup].
-_deserializeTransformerOrGroup(Map map, TransformerId id) {
-  if (map['type'] == 'Transformer') {
-    var transformer = new _ForeignTransformer(map);
-    return ExcludingTransformer.wrap(transformer, id.includes, id.excludes);
-  }
-
-  assert(map['type'] == 'TransformerGroup');
-  return new _ForeignGroup(id, map);
-}