Split dart:builtin into dart:builtin and dart:io.

tests/standalone/src/DirectoryInvalidArgumentsTest.dart

Index: tests/standalone/src/DirectoryInvalidArgumentsTest.dart
diff --git a/tests/standalone/src/DirectoryInvalidArgumentsTest.dart b/tests/standalone/src/DirectoryInvalidArgumentsTest.dart
index b83e191c64c97294cac8f3bd1a3912c023e958de..0b9b478e4bb386952966aa944cffb9338ddf1379 100644
--- a/tests/standalone/src/DirectoryInvalidArgumentsTest.dart
+++ b/tests/standalone/src/DirectoryInvalidArgumentsTest.dart
@@ -2,6 +2,8 @@
 // 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.
 
+#import("dart:io");
+
 class DirectoryInvalidArgumentsTest {
   static void testFailingList(Directory d, var recursive) {
     int errors = 0;