Add test directive to include other files used by a test in its compiled output directory.

tests/standalone/io/regress_21160_test.dart

 // Copyright (c) 2013, 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.
 
+// OtherResources=certificates/server_chain.pem
+// OtherResources=certificates/server_key.pem
+// OtherResources=certificates/trusted_certs.pem
+
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 import "package:async_helper/async_helper.dart";
 
 import "dart:async";
 import "dart:io";
 import "dart:typed_data";
 
 String localFile(path) => Platform.script.resolve(path).toFilePath();
 
@@ skipping 56 matching lines @@
     Expect.fail('Unexpected error: $e');
   }, onDone: () {
     Expect.equals(body.length, DATA.length);
     for (int i = 0; i < body.length; i++) {
       Expect.equals(body[i], DATA[i]);
     }
     server.close();
     asyncEnd();
   });
 }