Undo bogus change to use old dart:io API.

utils/tests/pub/test_pub.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.
 
 /**
  * Test infrastructure for testing pub. Unlike typical unit tests, most pub
  * tests are integration tests that stage some stuff on the file system, run
  * pub, and then validate the results. This library provides an API to build
  * tests like that.
  */
@@ skipping 1141 matching lines @@
     var sinkStream = new ListInputStream();
     var tempDir;
     // TODO(nweiz): propagate any errors to the return value. See issue 3657.
     createTempDir().chain((_tempDir) {
       tempDir = _tempDir;
       return create(tempDir);
     }).then((tar) {
       var sourceStream = tar.openInputStream();
       pipeInputToInput(sourceStream,
                        sinkStream,
-                       () => tempDir.deleteRecursively());
+                       () => tempDir.delete(recursive: true));
     });
     return sinkStream;
   }
 }
 
 /**
  * A descriptor that validates that no file exists with the given name.
  */
 class NothingDescriptor extends Descriptor {
   NothingDescriptor(String name) : super(name);
@@ skipping 51 matching lines @@
 }
 
 /**
  * Schedules a callback to be called after Pub is run with [runPub], even if it
  * fails.
  */
 void _scheduleCleanup(_ScheduledEvent event) {
   if (_scheduledCleanup == null) _scheduledCleanup = [];
   _scheduledCleanup.add(event);
 }