Clean-up of the system shutdown code paths

ash/system/date/date_default_view.cc

Index: ash/system/date/date_default_view.cc
diff --git a/ash/system/date/date_default_view.cc b/ash/system/date/date_default_view.cc
index 6b07e25e06177de0ea8ce46f09cb884a86092d5a..44cb9978d5b595c884bc18c87cb4292b7f1dac60 100644
--- a/ash/system/date/date_default_view.cc
+++ b/ash/system/date/date_default_view.cc
@@ -12,6 +12,7 @@
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_popup_header_button.h"
+#include "ash/wm/lock_state_controller.h"
 #include "grit/ash_resources.h"
 #include "grit/ash_strings.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -111,7 +112,8 @@ void DateDefaultView::ButtonPressed(views::Button* sender,
     tray_delegate->ShowHelp();
   } else if (sender == shutdown_) {
     shell->metrics()->RecordUserMetricsAction(ash::UMA_TRAY_SHUT_DOWN);
-    tray_delegate->ShutDown();
+    ash::Shell::GetInstance()->lock_state_controller()->RequestShutdown(
+        ash::LockStateController::POWER_OFF);
   } else if (sender == lock_) {
     shell->metrics()->RecordUserMetricsAction(ash::UMA_TRAY_LOCK_SCREEN);
     tray_delegate->RequestLockScreen();