[Ozone-Drm] Remove GPU lock

ui/ozone/platform/drm/gpu/gpu_lock.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 UI_OZONE_PLATFORM_DRM_GPU_GPU_LOCK_H_
-#define UI_OZONE_PLATFORM_DRM_GPU_GPU_LOCK_H_
-
-#include "base/macros.h"
-
-namespace ui {
-
-// Used to synchronize with Frecon and make sure the GPU process isn't trying to
-// access the DRM resources before Frecon finishes drawing.
-class GpuLock {
- public:
-  GpuLock();
-  ~GpuLock();
-
- private:
-  int fd_;
-
-  DISALLOW_COPY_AND_ASSIGN(GpuLock);
-};
-
-}  // namespace ui
-
-#endif  // UI_OZONE_PLATFORM_DRM_GPU_GPU_LOCK_H_