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

ui/views/mus/window_manager_connection.h

Index: ui/views/mus/window_manager_connection.h
diff --git a/ui/views/mus/window_manager_connection.h b/ui/views/mus/window_manager_connection.h
index 867e97b4522a1dcd7fe157b571c1a7c6d6441807..69291f7da625dc031173fbce3416d6393579d3ff 100644
--- a/ui/views/mus/window_manager_connection.h
+++ b/ui/views/mus/window_manager_connection.h
@@ -24,6 +24,10 @@ namespace shell {
 class Connector;
 }
 
+namespace ui {
+class GpuService;
+}
+
 namespace views {
 class ClipboardMus;
 class NativeWidget;
@@ -96,6 +100,7 @@ class VIEWS_MUS_EXPORT WindowManagerConnection
   shell::Identity identity_;
   std::unique_ptr<ScreenMus> screen_;
   std::unique_ptr<ui::WindowTreeClient> client_;
+  std::unique_ptr<ui::GpuService> gpu_service_;
   // Must be empty on destruction.
   base::ObserverList<PointerWatcher, true> pointer_watchers_;
   base::ObserverList<TouchEventWatcher, true> touch_event_watchers_;