Install barback from a hosted source in all tests.

test/dart2js/compiles_generated_file_from_dependency_outside_web_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.
 
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import '../serve/utils.dart';
 
 main() {
   // This is a regression test for issue #17198.
   integration("compiles a Dart file that imports a generated file to JS "
       "outside web/", () {
+    serveBarback();
+
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "version": "0.0.1",
-        "transformers": ["myapp/transformer"]
+        "transformers": ["myapp/transformer"],
+        "dependencies": {"barback": "any"}
       }),
       d.dir("lib", [
         d.file("transformer.dart", dartTransformer("munge"))
       ]),
       d.dir("test", [
         d.file("main.dart", """
 import "other.dart";
 void main() => print(TOKEN);
 """),
         d.file("other.dart", """
 library other;
 const TOKEN = "before";
 """)
-        ])
+      ])
     ]).create();
 
-    createLockFile('myapp', pkg: ['barback']);
-
+    pubGet();
     pubServe(args: ["test"]);
     requestShouldSucceed("main.dart.js", contains("(before, munge)"),
         root: "test");
     endPubServe();
   });
 }