Adding test for validating that formdata is sent.

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 24 matching lines @@
           resp.headers.set("Access-Control-Allow-Origin", "*");
           file.openInputStream().pipe(resp.outputStream);
         } else {
           resp.statusCode = HttpStatus.NOT_FOUND;
           resp.outputStream.close();
         }
       });
     }
   };
 
+  // Echos back the contents of the request as the response data.
+  _httpServer.addRequestHandler((req) => req.path == "/echo", (request, resp) {
+    resp.headers.set("Access-Control-Allow-Origin", "*");
+
+    request.inputStream.pipe(resp.outputStream);
+  });
+
   _httpServer.listen(host, port);
 }
 
 terminateHttpServer() {
   if (_httpServer != null) _httpServer.close();
 }