Move Show and Hide impls from PlatformWindowMus to NativeWidgetMus

ui/views/mus/platform_window_mus.cc

Index: ui/views/mus/platform_window_mus.cc
diff --git a/ui/views/mus/platform_window_mus.cc b/ui/views/mus/platform_window_mus.cc
index 79ca64c812ebb3985deca90be626a96500250f55..9f05d2df198894735f8dbe6e83d1152d45e6178c 100644
--- a/ui/views/mus/platform_window_mus.cc
+++ b/ui/views/mus/platform_window_mus.cc
@@ -116,13 +116,9 @@ void PlatformWindowMus::SetCursorById(mus::mojom::Cursor cursor) {
   }
 }
 
-void PlatformWindowMus::Show() {
-  mus_window_->SetVisible(true);
-}
+void PlatformWindowMus::Show() {}
 
-void PlatformWindowMus::Hide() {
-  mus_window_->SetVisible(false);
-}
+void PlatformWindowMus::Hide() {}
 
 void PlatformWindowMus::Close() {
   NOTIMPLEMENTED();