Install barback from a hosted source in all tests.

test/transformer/exclusion/works_on_dart2js_test.dart

 // Copyright (c) 2014, 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 'package:scheduled_test/scheduled_stream.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 import '../../serve/utils.dart';
 
 main() {
   integration("works on the dart2js transformer", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "transformers": [
           {
             "\$dart2js": {
               "\$include": ["web/a.dart", "web/b.dart"],
               "\$exclude": "web/a.dart"
             }
           }
-        ]
+        ],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("web", [
         d.file("a.dart", "void main() => print('hello');"),
         d.file("b.dart", "void main() => print('hello');"),
         d.file("c.dart", "void main() => print('hello');")
       ])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
+    pubGet();
     var server = pubServe();
     // Dart2js should remain lazy.
     server.stdout.expect("Build completed successfully");
 
     requestShould404("a.dart.js");
     requestShouldSucceed("b.dart.js", isNot(isEmpty));
     server.stdout.expect(consumeThrough(emitsLines(
         "[Info from Dart2JS]:\n"
         "Compiling myapp|web/b.dart...")));
     server.stdout.expect(consumeThrough("Build completed successfully"));
 
     requestShould404("c.dart.js");
     endPubServe();
   });
 }