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

tests/standalone/io/process_check_arguments_test.dart

Index: tests/standalone/io/process_check_arguments_test.dart
diff --git a/tests/standalone/io/process_check_arguments_test.dart b/tests/standalone/io/process_check_arguments_test.dart
index 1e97c8d7a20593ed2262031e9dbdde53875458b5..b636bb8c5b79cb51de45eb5a9dad712674467955 100644
--- a/tests/standalone/io/process_check_arguments_test.dart
+++ b/tests/standalone/io/process_check_arguments_test.dart
@@ -2,8 +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");
-#source("process_test_util.dart");
+import "dart:io";
+part "process_test_util.dart";
 
 test(args) {
   var future = Process.start(new Options().executable, args);