Fix remaining uses of Directory.systemTemp outside test scripts.

tests/standalone/io/file_fuzz_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.
 
 // 'fuzz' test the file APIs by providing unexpected type arguments. The test
 // passes if the VM does not crash.
 
 import 'dart:async';
 import 'dart:io';
 
@@ skipping 70 matching lines @@
     for (var p in typePermutations(3)) {
       doItSync(() => opened.readIntoSync(p[0], p[1], p[2]));
       doItSync(() => opened.writeFromSync(p[0], p[1], p[2]));
     }
     opened.closeSync();
   }
   temp.deleteSync(recursive: true);
 }
 
 fuzzAsyncRandomAccessMethods() {
-  var d = new Directory('');
   var temp = Directory.systemTemp.createTempSync('dart_file_fuzz');
   var file = new File('${temp.path}/x');
   file.createSync();
   var modes = [ FileMode.READ, FileMode.WRITE, FileMode.APPEND ];
   var futures = [];
   var openedFiles = [];
   for (var m in modes) {
     var opened = file.openSync(mode: m);
     openedFiles.add(opened);
     typeMapping.forEach((k, v) {
@@ skipping 16 matching lines @@
     temp.deleteSync(recursive: true);
   });
 }
 
 main() {
   fuzzSyncMethods();
   fuzzAsyncMethods();
   fuzzSyncRandomAccessMethods();
   fuzzAsyncRandomAccessMethods();
 }