Use Directory.systemTemp getter in pkg subdirectory of repository.

pkg/scheduled_test/test/descriptor/utils.dart

 // Copyright (c) 2013, 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.
 
 library test.descriptor.utils;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:scheduled_test/descriptor.dart' as d;
 import 'package:scheduled_test/scheduled_test.dart';
 
 export '../utils.dart';
 
 String sandbox;
 
 void scheduleSandbox() {
   schedule(() {
-    return new Directory('').createTemp().then((dir) {
+    return Directory.systemTemp.createTemp('descriptor_sandbox_').then((dir) {
       sandbox = dir.path;
       d.defaultRoot = sandbox;
     });
   });
 
   currentSchedule.onComplete.schedule(() {
     d.defaultRoot = null;
     if (sandbox == null) return;
     var oldSandbox = sandbox;
     sandbox = null;
     return new Directory(oldSandbox).delete(recursive: true);
   });
 }
 
 Future<List<int>> byteStreamToList(Stream<List<int>> stream) {
   return stream.fold(<int>[], (buffer, chunk) {
     buffer.addAll(chunk);
     return buffer;
   });
 }
 
 Future<String> byteStreamToString(Stream<List<int>> stream) =>
   byteStreamToList(stream).then((bytes) => new String.fromCharCodes(bytes));