Simplify the organization of //mojo_file_utils.

mojo/file_utils/tests/file_util_test_base.h

-// 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.
-
-#ifndef MOJO_FILE_UTILS_TESTS_FILE_UTIL_TEST_BASE_H_
-#define MOJO_FILE_UTILS_TESTS_FILE_UTIL_TEST_BASE_H_
-
-#include "mojo/public/cpp/application/application_test_base.h"
-#include "mojo/public/cpp/system/macros.h"
-#include "mojo/services/files/interfaces/files.mojom.h"
-
-namespace file_utils {
-namespace test {
-
-class FileUtilTestBase : public mojo::test::ApplicationTestBase {
- public:
-  FileUtilTestBase();
-  ~FileUtilTestBase() override;
-
-  void SetUp() override;
-
- protected:
-  mojo::files::FilesPtr& files() { return files_; }
-
- private:
-  mojo::files::FilesPtr files_;
-
-  MOJO_DISALLOW_COPY_AND_ASSIGN(FileUtilTestBase);
-};
-
-}  // namespace test
-}  // namespace file_utils
-
-#endif  // MOJO_FILE_UTILS_TESTS_FILE_UTIL_TEST_BASE_H_