Dart: Reorganize files

mojo/dart/unittests/embedder_tests/shared_buffer_finalizer_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 'dart:convert';
 
 import 'package:mojo/bindings.dart';
@@ skipping 15 matching lines @@
 int main() {
   MojoSharedBuffer bufferHandle;
 
   for (int i = 0; i < 1000; i++) {
     bufferHandle = new MojoSharedBuffer.create(30000);
     mapAndAccess(bufferHandle, 30000);
   }
 
   return 0;
 }