mus: Changes SetDisplayRoot() to create actual display

services/ui/display/screen_manager_ozone_internal.cc

Index: services/ui/display/screen_manager_ozone_internal.cc
diff --git a/services/ui/display/screen_manager_ozone_internal.cc b/services/ui/display/screen_manager_ozone_internal.cc
index 854ef3ae7bd45eda057238498017c3cad4e73b21..63ca244496951c8ccacd04973f76272ae689fb21 100644
--- a/services/ui/display/screen_manager_ozone_internal.cc
+++ b/services/ui/display/screen_manager_ozone_internal.cc
@@ -170,6 +170,10 @@ void ScreenManagerOzoneInternal::RequestCloseDisplay(int64_t display_id) {
   fake_display_controller_->RemoveDisplay(display_id);
 }
 
+display::ScreenBase* ScreenManagerOzoneInternal::GetScreen() {
+  return screen_;
+}
+
 void ScreenManagerOzoneInternal::ToggleAddRemoveDisplay() {
   if (!fake_display_controller_)
     return;