mash: remove more shell/shelf WmWindow usage.

ash/wm/system_modal_container_layout_manager_unittest.cc

Index: ash/wm/system_modal_container_layout_manager_unittest.cc
diff --git a/ash/wm/system_modal_container_layout_manager_unittest.cc b/ash/wm/system_modal_container_layout_manager_unittest.cc
index a3c10da8320fc864cf45cd34f26ff8625d21f0cf..e87a676dc1b9dd8e98b2a14b59e5b2fa221478f8 100644
--- a/ash/wm/system_modal_container_layout_manager_unittest.cc
+++ b/ash/wm/system_modal_container_layout_manager_unittest.cc
@@ -801,9 +801,8 @@ TEST_F(SystemModalContainerLayoutManagerTest, VisibilityChange) {
                                              CurrentContext())
           ->GetNativeWindow());
   SystemModalContainerLayoutManager* layout_manager =
-      ShellPort::Get()
-          ->GetPrimaryRootWindowController()
-          ->GetSystemModalLayoutManager(modal_window.get());
+      Shell::GetPrimaryRootWindowController()->GetSystemModalLayoutManager(
+          modal_window.get());
 
   EXPECT_FALSE(ShellPort::Get()->IsSystemModalWindowOpen());
   EXPECT_FALSE(layout_manager->has_window_dimmer());