Add support for directory renaming to dart:io.

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:io");
 #import("dart:isolate");
 
 class DirectoryTest {
@@ skipping 389 matching lines @@
 testCreateTempError() {
   var location = illegalTempDirectoryLocation();
   if (location == null) return;
 
   var port = new ReceivePort();
   var future = new Directory(location).createTemp();
   future.handleException((e) => port.close());
 }
 
 
+testRename() {
+  var d = new Directory('');
+  var temp1 = d.createTempSync();
+  var temp2 = d.createTempSync();
+  var temp3 = temp1.renameSync(temp2.path);
+  Expect.isFalse(temp1.existsSync());
+  Expect.isTrue(temp2.existsSync());
+  Expect.equals(temp3.path, temp2.path);
+
+  temp2.rename(temp1.path).then((temp4) {
+    Expect.isFalse(temp3.existsSync());
+    Expect.isFalse(temp2.existsSync());
+    Expect.isTrue(temp1.existsSync());
+    Expect.isTrue(temp4.existsSync());
+    Expect.equals(temp1.path, temp4.path);
+    temp1.deleteRecursivelySync();
+  });
+}
+
+
 main() {
   DirectoryTest.testMain();
   NestedTempDirectoryTest.testMain();
   testCreateTempErrorSync();
   testCreateTempError();
+  testRename();
 }