Modify tests to use Directory.systemTemp

tests/standalone/io/file_error_test.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.
 //
 // Dart test program for testing error handling in file I/O.
 
 import "dart:convert";
 import "dart:io";
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
 
 Directory tempDir() {
-  return new Directory('').createTempSync();
+  return Directory.systemTemp.createTempSync('dart_file_error');
 }
 
 
 bool checkNonExistentFileException(e, str) {
   Expect.isTrue(e is FileException);
   Expect.isTrue(e.osError != null);
   Expect.isTrue(e.toString().indexOf(str) != -1);
   // File not not found has error code 2 on all supported platforms.
   Expect.equals(2, e.osError.errorCode);
   return true;
@@ skipping 405 matching lines @@
   testReadAsLinesNonExistent();
   testWriteByteToReadOnlyFile();
   testWriteFromToReadOnlyFile();
   testTruncateReadOnlyFile();
   testOperateOnClosedFile();
   testRepeatedlyCloseFile();
   testRepeatedlyCloseFileSync();
   testReadSyncBigInt();
   testReadSyncClosedFile();
 }