Use Directory.systemTemp getter in pkg subdirectory of repository.

pkg/watcher/test/utils.dart

 // Copyright (c) 2012, 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 watcher.test.utils;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ skipping 28 matching lines @@
 void initConfig() {
   useCompactVMConfiguration();
   filterStacks = true;
 }
 
 /// Creates the sandbox directory the other functions in this library use and
 /// ensures it's deleted when the test ends.
 ///
 /// This should usually be called by [setUp].
 void createSandbox() {
-  var dir = new Directory("").createTempSync();
+  var dir = Directory.systemTemp.createTempSync('watcher_test_');
   _sandboxDir = dir.path;
 
   _mockFileModificationTimes = new Map<String, int>();
   mockGetModificationTime((path) {
     path = p.normalize(p.relative(path, from: _sandboxDir));
 
     // Make sure we got a path in the sandbox.
     assert(p.isRelative(path)  && !path.startsWith(".."));
 
     return new DateTime.fromMillisecondsSinceEpoch(
@@ skipping 160 matching lines @@
 
   Description describe(Description description) {
     description.add("$type $path");
   }
 
   bool matches(item, Map matchState) =>
       item is WatchEvent &&
       item.type == type &&
       p.normalize(item.path) == p.normalize(path);
 }