Support passing configuration data to a transformer plugin.

sdk/lib/_internal/pub/test/serve/utils.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 pub_tests;
 
 import 'dart:async';
 
 import 'package:http/http.dart' as http;
 import 'package:scheduled_test/scheduled_process.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../test_pub.dart';
 
 /// The pub process running "pub serve".
 ScheduledProcess _pubServer;
 
 /// The ephemeral port assigned to the running server.
 int _port;
 
 /// The code for a transformer that renames ".txt" files to ".out" and adds a
 /// ".out" suffix.
 const REWRITE_TRANSFORMER = """
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 
 class RewriteTransformer extends Transformer {
-  RewriteTransformer();
+  RewriteTransformer.asPlugin();
 
   String get allowedExtensions => '.txt';
 
   Future apply(Transform transform) {
     return transform.primaryInput.readAsString().then((contents) {
       var id = transform.primaryInput.id.changeExtension(".out");
       transform.addOutput(new Asset.fromString(id, "\$contents.out"));
     });
   }
 }
@@ skipping 22 matching lines @@
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 $import
 
 const TOKEN = "$id";
 
 final _tokenRegExp = new RegExp(r'^const TOKEN = "(.*?)";\$', multiLine: true);
 
 class DartTransformer extends Transformer {
-  DartTransformer();
+  DartTransformer.asPlugin();
 
   String get allowedExtensions => '.dart';
 
   Future apply(Transform transform) {
     return transform.primaryInput.readAsString().then((contents) {
       transform.addOutput(new Asset.fromString(transform.primaryInput.id,
           contents.replaceAllMapped(_tokenRegExp, (match) {
         return 'const TOKEN = "(\${match[1]}, \$TOKEN)";';
       })));
     });
@@ skipping 76 matching lines @@
     return _pubServer.nextLine().then((line) {
       if (line.contains("successfully")) return;
 
       // This line wasn't it, so ignore it and keep trying.
       return nextLine();
     });
   }
 
   schedule(nextLine);
 }