chromeos: Migrate SignOut and RequestRestartForUpdate to mojo interface

ash/common/system/update/tray_update.cc

Index: ash/common/system/update/tray_update.cc
diff --git a/ash/common/system/update/tray_update.cc b/ash/common/system/update/tray_update.cc
index b887232d2f93f628f2ba293bcfac90d810f280ec..42ed546ecab0463776585b647c09eb9e09953017 100644
--- a/ash/common/system/update/tray_update.cc
+++ b/ash/common/system/update/tray_update.cc
@@ -8,6 +8,7 @@
 #include "ash/common/metrics/user_metrics_action.h"
 #include "ash/common/system/tray/fixed_sized_image_view.h"
 #include "ash/common/system/tray/system_tray.h"
+#include "ash/common/system/tray/system_tray_controller.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/system/tray/system_tray_notifier.h"
 #include "ash/common/system/tray/tray_constants.h"
@@ -119,7 +120,7 @@ class UpdateView : public ActionableView {
  private:
   // Overridden from ActionableView.
   bool PerformAction(const ui::Event& event) override {
-    WmShell::Get()->system_tray_delegate()->RequestRestartForUpdate();
+    WmShell::Get()->system_tray_controller()->RequestRestartForUpdate();
     WmShell::Get()->RecordUserMetricsAction(
         UMA_STATUS_AREA_OS_UPDATE_DEFAULT_SELECTED);
     CloseSystemBubble();