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

tests/standalone/io/http_proxy_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:convert/convert.dart";
 import "package:crypto/crypto.dart";
 import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import 'dart:convert';
 
 String localFile(path) => Platform.script.resolve(path).toFilePath();
 
 SecurityContext serverContext = new SecurityContext()
@@ skipping 440 matching lines @@
   });
   });
 }
 
 main() {
   testInvalidProxy();
   testDirectProxy();
   testProxy();
   testProxyChain();
 }