Make lazy and declaring transformers work with $include/$exclude.

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 'dart:convert';
 import 'dart:io';
 
@@ skipping 39 matching lines @@
 
   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"));
     });
   }
 }
 """;
 
+/// The code for a lazy version of [REWRITE_TRANSFORMER].
+const LAZY_TRANSFORMER = """
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+
+class LazyRewriteTransformer extends Transformer implements LazyTransformer {
+  LazyRewriteTransformer.asPlugin();
+
+  String get allowedExtensions => '.txt';
+
+  Future apply(Transform transform) {
+    transform.logger.info('Rewriting \${transform.primaryInput.id}.');
+    return transform.primaryInput.readAsString().then((contents) {
+      var id = transform.primaryInput.id.changeExtension(".out");
+      transform.addOutput(new Asset.fromString(id, "\$contents.out"));
+    });
+  }
+
+  Future declareOutputs(DeclaringTransform transform) {
+    transform.declareOutput(transform.primaryId.changeExtension(".out"));
+    return new Future.value();
+  }
+}
+""";
+
 /// The web socket error code for a directory not being served.
 const NOT_SERVED = 1;
 
 /// Returns the source code for a Dart library defining a Transformer that
 /// rewrites Dart files.
 ///
 /// The transformer defines a constant named TOKEN whose value is [id]. When the
 /// transformer transforms another Dart file, it will look for a "TOKEN"
 /// constant definition there and modify it to include *this* transformer's
 /// TOKEN value as well.
@@ skipping 371 matching lines @@
 /// included. Unlike [getServerUrl], this should only be called after the ports
 /// are known.
 String _getServerUrlSync([String root, String path]) {
   if (root == null) root = 'web';
   expect(_ports, contains(root));
   var url = "http://127.0.0.1:${_ports[root]}";
   if (path != null) url = "$url/$path";
   return url;
 }