Move scoped_test_dir.* and test_io_thread.* from edk/test to edk/system/test.

mojo/edk/test/scoped_test_dir.cc

-// 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.
-
-#include "mojo/edk/test/scoped_test_dir.h"
-
-#include "base/files/file_path.h"
-#include "base/files/file_util.h"
-#include "base/logging.h"
-
-namespace mojo {
-namespace test {
-
-ScopedTestDir::ScopedTestDir() {
-  CHECK(temp_dir_.CreateUniqueTempDir());
-}
-
-ScopedTestDir::~ScopedTestDir() {}
-
-util::ScopedFILE ScopedTestDir::CreateFile() {
-  base::FilePath unused;
-  return util::ScopedFILE(
-      base::CreateAndOpenTemporaryFileInDir(temp_dir_.path(), &unused));
-}
-
-}  // namespace test
-}  // namespace mojo