Unify mustash display closing code paths.

services/ui/ws/platform_display.cc

Index: services/ui/ws/platform_display.cc
diff --git a/services/ui/ws/platform_display.cc b/services/ui/ws/platform_display.cc
index 74f92c142666fb9fa83c4dfc2e298d4911da31c7..6a082d23af54525b8fe78086e153d92950b71802 100644
--- a/services/ui/ws/platform_display.cc
+++ b/services/ui/ws/platform_display.cc
@@ -255,13 +255,10 @@ void DefaultPlatformDisplay::DispatchEvent(ui::Event* event) {
 }
 
 void DefaultPlatformDisplay::OnCloseRequest() {
-  platform_window_->Close();
+  display::PlatformScreen::GetInstance()->RequestCloseDisplay(GetId());
 }
 
-void DefaultPlatformDisplay::OnClosed() {
-  if (delegate_)
-    delegate_->OnDisplayClosed();
-}
+void DefaultPlatformDisplay::OnClosed() {}
 
 void DefaultPlatformDisplay::OnWindowStateChanged(
     ui::PlatformWindowState new_state) {}