Dart: Reorganize files

mojo/dart/unittests/embedder_tests/control_messages_test.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:async';
 import 'dart:isolate';
 import 'dart:typed_data';
 
 import 'package:mojo/bindings.dart' as bindings;
 import 'package:mojo/core.dart' as core;
@@ skipping 86 matching lines @@
   }
   Expect.isTrue(exceptionCaught);
   closeProxyAndStub(ps);
 }
 
 main() async {
   await testQueryVersion();
   await testRequireVersionSuccess();
   await testRequireVersionDisconnect();
 }