Revert of services/ui: Have an explicit lifetime/ownership of ui::GpuService.

ash/mus/window_manager_application.h

Index: ash/mus/window_manager_application.h
diff --git a/ash/mus/window_manager_application.h b/ash/mus/window_manager_application.h
index 4d08dd83eeef9b841b6b926207c150da0c0a114c..a678f35609472e777f6d5c8e4dfe3a7bf4996913 100644
--- a/ash/mus/window_manager_application.h
+++ b/ash/mus/window_manager_application.h
@@ -28,7 +28,6 @@
 
 namespace ui {
 class Event;
-class GpuService;
 class WindowTreeClient;
 }
 
@@ -109,7 +108,6 @@
   std::vector<mojo::InterfaceRequest<mojom::UserWindowController>>
       user_window_controller_requests_;
 
-  std::unique_ptr<ui::GpuService> gpu_service_;
   std::unique_ptr<WindowManager> window_manager_;
 
   std::set<AcceleratorRegistrarImpl*> accelerator_registrars_;