mash: Implement restore on item click.

ash/mus/user_window_controller_impl.cc

Index: ash/mus/user_window_controller_impl.cc
diff --git a/ash/mus/user_window_controller_impl.cc b/ash/mus/user_window_controller_impl.cc
index ba64ffb28ace09ad43fa964046a5aac559bf2750..365acc74aa83aaa9ac68c40f14f83e07abdb849f 100644
--- a/ash/mus/user_window_controller_impl.cc
+++ b/ash/mus/user_window_controller_impl.cc
@@ -197,10 +197,12 @@ void UserWindowControllerImpl::AddUserWindowObserver(
   user_window_observer_->OnUserWindowObserverAdded(std::move(user_windows));
 }
 
-void UserWindowControllerImpl::FocusUserWindow(uint32_t window_id) {
+void UserWindowControllerImpl::ActivateUserWindow(uint32_t window_id) {
   ::ui::Window* window = GetUserWindowById(window_id);
-  if (window)
+  if (window) {
+    window->SetVisible(true);
     window->SetFocus();
+  }
 }
 
 }  // namespace mus