Add cross-origin test with credentials.

tools/testing/dart/http_server.dart

 // Copyright (c) 2012, 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.
 
 library http_server;
 
 import 'dart:io';
 import 'dart:isolate';
 import 'test_suite.dart';  // For TestUtils.
 
@@ skipping 14 matching lines @@
     if (!requestPath.isAbsolute) {
       resp.statusCode = HttpStatus.NOT_FOUND;
       resp.outputStream.close();
     } else {
       var path = basePath;
       requestPath.segments().forEach((s) => path = path.append(s));
       var file = new File(path.toNativePath());
       file.exists().then((exists) {
         if (exists) {
           // Allow loading from localhost in browsers.
-          resp.headers.set("Access-Control-Allow-Origin", "*");
+          resp.headers.set("Access-Control-Allow-Origin", "file://");
+          resp.headers.set('Access-Control-Allow-Credentials', 'true');
           file.openInputStream().pipe(resp.outputStream);
         } else {
           resp.statusCode = HttpStatus.NOT_FOUND;
           resp.outputStream.close();
         }
       });
     }
   };
 
   _httpServer.listen(host, port);
 }
 
 terminateHttpServer() {
   if (_httpServer != null) _httpServer.close();
 }