Reorganize tests for samples so the test is discoverable from the sample

samples/chat/test/chat_server_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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
-import "package:expect/expect.dart";
 import 'dart:io';
 import 'dart:isolate';
-import "dart:convert";
-import '../../../chat/chat_server_lib.dart';
+import 'dart:convert';
+import 'package:expect/expect.dart';
+import '../chat_server_lib.dart';
 
 // Message to start chat test client running in an isolate.
 class ChatTestClientStart {
   ChatTestClientStart(int this.totalClients,
                       int this.messagesToSend,
                       int this.messagesToReceive,
                       int this.port);
 
   int totalClients;
   int messagesToSend;
@@ skipping 286 matching lines @@
   TestMain testMain = new TestMain.run(10, 2);
 }
 
 
 void main() {
   testOneClient();
   testTwoClients();
   testTwoClientsMoreMessages();
   testTenClients();
 }