Make servePackages's contents argument saner.

sdk/lib/_internal/pub/test/global/deactivate/hosted_package_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS 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 '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('deactivates an active hosted package', () {
-    servePackages([
-      packageMap("foo", "1.0.0")
-    ]);
+    servePackages((builder) => builder.serve("foo", "1.0.0"));
 
     schedulePub(args: ["global", "activate", "foo"]);
 
     schedulePub(args: ["global", "deactivate", "foo"],
         output: "Deactivated package foo 1.0.0.");
   });
 }