Use "package:" imports for pub.

test/serve/gets_first_if_dependency_is_not_installed_test.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 'package:path/path.dart' as path;
+import 'package:pub/src/io.dart';
 import 'package:scheduled_test/scheduled_test.dart';
 
-import '../../lib/src/io.dart';
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
 import 'utils.dart';
 
 main() {
   initConfig();
   integration("gets first if a dependency is not installed", () {
     servePackages((builder) => builder.serve("foo", "1.2.3"));
 
     d.appDir({"foo": "1.2.3"}).create();
 
     // Run pub to get a lock file.
     pubGet();
 
     // Delete the system cache so it isn't installed any more.
     schedule(() => deleteEntry(path.join(sandboxDir, cachePath)));
 
     pubServe(shouldGetFirst: true);
     requestShouldSucceed("packages/foo/foo.dart", 'main() => "foo 1.2.3";');
     endPubServe();
   });
 }