ui: Cleanup class/struct forward declarations

ui/ozone/platform/drm/host/drm_window_host.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_HOST_DRM_WINDOW_HOST_H_
 #define UI_OZONE_PLATFORM_DRM_HOST_DRM_WINDOW_HOST_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/display/types/display_snapshot.h"
 #include "ui/events/platform/platform_event_dispatcher.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/ozone/platform/drm/host/gpu_thread_observer.h"
 #include "ui/platform_window/platform_window.h"
 
 namespace ui {
 
 class DrmDisplayHostManager;
 class DrmCursor;
-class DrmGpuWindow;
 class DrmOverlayManager;
 class DrmWindowHostManager;
 class EventFactoryEvdev;
 class GpuThreadAdapter;
+class PlatformWindowDelegate;
 
 // Implementation of the platform window. This object and its handle |widget_|
 // uniquely identify a window. Since the DRI/GBM platform is split into 2
 // pieces (Browser process and GPU process), internally we need to make sure the
 // state is synchronized between the 2 processes.
 //
 // |widget_| is used in both processes to uniquely identify the window. This
 // means that any state on the browser side needs to be propagated to the GPU.
 // State propagation needs to happen before the state change is acknowledged to
 // |delegate_| as |delegate_| is responsible for initializing the surface
@@ skipping 60 matching lines @@
   gfx::AcceleratedWidget widget_;
 
   gfx::Rect cursor_confined_bounds_;
 
   DISALLOW_COPY_AND_ASSIGN(DrmWindowHost);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_HOST_DRM_WINDOW_HOST_H_