Modify tests to use Directory.systemTemp

tests/standalone/io/skipping_dart2js_compilations_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.
 
 /*
  * This test makes sure that the "skipping Dart2Js compilations if the output is
  * already up to date" feature does work as it should.
  * Therefore this test ensures that compilations are only skipped if the last
  * modified date of the output of a dart2js compilation is newer than
  *   - the the dart application to compile (including it's dependencies)
@@ skipping 20 matching lines @@
   Directory tempDir;
   File testJs;
   File testJsDeps;
   File testDart;
   File testSnapshot;
 
   FileUtils({bool createJs,
              bool createJsDeps,
              bool createDart,
              bool createSnapshot}) {
-    tempDir = new Directory('').createTempSync();
+    tempDir = Directory.systemTemp
+                       .createTempSync('dart_skipping_dart2js_compilations');
     if (createJs) {
       testJs = _createFile(testJsFilePath);
       _writeToFile(testJs, "test.js content");
     }
     if (createSnapshot) {
       testSnapshot = _createFile(testSnapshotFilePath);
       _writeToFile(testSnapshot, "dart2js snapshot");
     }
     if (createDart) {
       testDart = _createFile(testDartFilePath);
@@ skipping 182 matching lines @@
       cleanup();
       throw error;
     }).then((_) {
       cleanup();
     });
   }
   // We need to wait some time to make sure that the files we 'touch' get a
   // bigger timestamp than the old ones
   new Timer(new Duration(seconds: 1), touchFilesAndRunTests);
 }