Remove old #import, #source, and #library syntax from tests/standalone.

tests/standalone/io/test_extension_fail_tester.dart

Index: tests/standalone/io/test_extension_fail_tester.dart
diff --git a/tests/standalone/io/test_extension_fail_tester.dart b/tests/standalone/io/test_extension_fail_tester.dart
index 8406c0a6a76f527e69926a90f83fb1af930011fc..628d8048bb8c6450945f96dfce1fbb45b33b7427 100644
--- a/tests/standalone/io/test_extension_fail_tester.dart
+++ b/tests/standalone/io/test_extension_fail_tester.dart
@@ -2,10 +2,10 @@
 // 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.
 
-#library("test_extension_test");
+library test_extension_test;
 
-#import("dart:isolate");
-#import('test_extension.dart');
+import "dart:isolate";
+import "test_extension.dart";
 
 main() {
   try {