dart:io | Add Directory.CreateSystemTemp(template) and change Directory.CreateTemp(template).

tests/standalone/io/directory_test.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.
 //
 // Directory listing test.
 
 import "dart:async";
 import "dart:io";
 
 import "package:async_helper/async_helper.dart";
@@ skipping 434 matching lines @@
       : createdDirectories = new List<Directory>() {
     new Directory("").createTemp().then(createPhaseCallback);
   }
 
   void createPhaseCallback(temp) {
     createdDirectories.add(temp);
     int nestingDepth = 6;
     var os = Platform.operatingSystem;
     if (os == "windows") nestingDepth = 2;
     if (createdDirectories.length < nestingDepth) {
-      temp = new Directory(
-          '${temp.path}/nested_temp_dir_${createdDirectories.length}_');
-      temp.createTemp().then(createPhaseCallback);
+      temp.createTemp('nested_temp_dir_${createdDirectories.length}_')
+          .then(createPhaseCallback);
     } else {
       deletePhaseCallback();
     }
   }
 
   void deletePhaseCallback() {
     if (!createdDirectories.isEmpty) {
       current = createdDirectories.removeLast();
       current.deleteSync();
       deletePhaseCallback();
@@ skipping 166 matching lines @@
   testCreateTempErrorSync();
   testCreateTempError();
   testCreateExistingSync();
   testCreateExisting();
   testCreateDirExistingFileSync();
   testCreateDirExistingFile();
   testCreateRecursive();
   testCreateRecursiveSync();
   testRename();
 }