Fix recursive directory-deletion of top-level files/links.

tests/standalone/io/directory_error_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.
 //
 // Dart test program for testing error handling in directory I/O.
 
 import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
@@ skipping 77 matching lines @@
     checkDeleteNonExistentFileException(e.error);
     done();
   });
 }
 
 
 bool checkDeleteRecursivelyNonExistentFileException(e) {
   Expect.isTrue(e is DirectoryIOException);
   Expect.isTrue(e.osError != null);
   Expect.isTrue(e.toString().indexOf("Deletion failed") != -1);
-  if (Platform.operatingSystem == "linux") {
-    Expect.equals(2, e.osError.errorCode);
-  } else if (Platform.operatingSystem == "macos") {
-    Expect.equals(2, e.osError.errorCode);
-  } else if (Platform.operatingSystem == "windows") {
-    Expect.equals(3, e.osError.errorCode);
-  }
+  // File not not found has error code 2 on all supported platforms.
+  Expect.equals(2, e.osError.errorCode);
 
   return true;
 }
 
 
 void testDeleteRecursivelyNonExistent(Directory temp, Function done) {
   Directory nonExistent = new Directory("${temp.path}/nonExistent");
   Expect.throws(() => nonExistent.deleteSync(recursive: true),
                 (e) => checkDeleteRecursivelyNonExistentFileException(e));
 
@@ skipping 104 matching lines @@
 main() {
   runTest(testCreateInNonExistent);
   runTest(testCreateTempInNonExistent);
   runTest(testDeleteNonExistent);
   runTest(testDeleteRecursivelyNonExistent);
   runTest(testListNonExistent);
   runTest(testRenameNonExistent);
   runTest(testRenameFileAsDirectory);
   runTest(testRenameOverwriteFile);
 }