ui: Cleanup class/struct forward declarations

ui/ozone/platform/drm/gpu/drm_thread_proxy.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_DRM_THREAD_PROXY_H_
 #define UI_OZONE_PLATFORM_DRM_GPU_DRM_THREAD_PROXY_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "ui/ozone/platform/drm/gpu/drm_thread.h"
 #include "ui/ozone/public/interfaces/device_cursor.mojom.h"
 
-namespace service_manager {
-class Connection;
-}
-
 namespace ui {
 
 class DrmWindowProxy;
 class InterThreadMessagingProxy;
 
 // Mediates the communication between GPU main/IO threads and the DRM thread. It
 // serves proxy objects that are safe to call on the GPU threads. The proxy
 // objects then deal with safely posting the messages to the DRM thread.
 class DrmThreadProxy {
  public:
@@ skipping 24 matching lines @@
 
  private:
   DrmThread drm_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(DrmThreadProxy);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRM_GPU_DRM_THREAD_PROXY_H_