[Ozone-DRI] Remove the extra helper thread and reuse the IO one

ui/ozone/platform/dri/dri_helper_thread.cc

Index: ui/ozone/platform/dri/dri_helper_thread.cc
diff --git a/ui/ozone/platform/dri/dri_helper_thread.cc b/ui/ozone/platform/dri/dri_helper_thread.cc
deleted file mode 100644
index 4ca33017e74c0153fbf4c22b6351bfb4a94fdb6a..0000000000000000000000000000000000000000
--- a/ui/ozone/platform/dri/dri_helper_thread.cc
+++ /dev/null
@@ -1,23 +0,0 @@
-// 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 "ui/ozone/platform/dri/dri_helper_thread.h"
-
-namespace ui {
-
-DriHelperThread::DriHelperThread() : Thread("DriHelperThread") {
-}
-
-DriHelperThread::~DriHelperThread() {
-  Stop();
-}
-
-void DriHelperThread::Initialize() {
-  DCHECK(!IsRunning());
-
-  if (!StartWithOptions(base::Thread::Options(base::MessageLoop::TYPE_IO, 0)))
-    LOG(FATAL) << "Failed to start the IO helper thread";
-}
-
-}  // namespace ui