ui: Cleanup class/struct forward declarations

ui/ozone/platform/drm/gpu/drm_device.h

 // Copyright 2014 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_DRM_DEVICE_H_
 #define UI_OZONE_PLATFORM_DRM_GPU_DRM_DEVICE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <vector>
 
 #include "base/callback.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
 #include "ui/gfx/overlay_transform.h"
 #include "ui/ozone/platform/drm/common/scoped_drm_types.h"
 #include "ui/ozone/platform/drm/gpu/hardware_display_plane_manager.h"
 
 typedef struct _drmEventContext drmEventContext;
 typedef struct _drmModeModeInfo drmModeModeInfo;
 
 struct SkImageInfo;
 
-namespace base {
-class SingleThreadTaskRunner;
-}  // namespace base
-
 namespace ui {
 
 class HardwareDisplayPlaneManager;
 struct GammaRampRGBEntry;
 
 // Wraps DRM calls into a nice interface. Used to provide different
 // implementations of the DRM calls. For the actual implementation the DRM API
 // would be called. In unit tests this interface would be stubbed.
 class DrmDevice : public base::RefCountedThreadSafe<DrmDevice> {
  public:
@@ skipping 161 matching lines @@
   std::unique_ptr<IOWatcher> watcher_;
 
   bool is_primary_device_;
 
   DISALLOW_COPY_AND_ASSIGN(DrmDevice);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_GPU_DRM_DEVICE_H_