[Ozone-Dri] Decouple the IO helper thread from DriWrapper

ui/ozone/platform/dri/dri_helper_thread.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 "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