Dart: Reorganize files

mojo/dart/test/async_await_test.dart

Index: mojo/dart/test/async_await_test.dart
diff --git a/mojo/dart/test/async_await_test.dart b/mojo/dart/test/async_await_test.dart
deleted file mode 100644
index 41d136a2fd14d1fcaec39bc6588a74e585b7e18b..0000000000000000000000000000000000000000
--- a/mojo/dart/test/async_await_test.dart
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright 2014 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 'package:mojo/core.dart';
-
-main() async {
-  var x = await (new Future.value(42));
-  assert(x == 42);
-}