chromeos: Migrate SignOut and RequestRestartForUpdate to mojo interface

ash/common/system/chromeos/session/logout_button_tray.cc

Index: ash/common/system/chromeos/session/logout_button_tray.cc
diff --git a/ash/common/system/chromeos/session/logout_button_tray.cc b/ash/common/system/chromeos/session/logout_button_tray.cc
index 25fdb936e121ec2c25ee09547726525b73728a53..5a49becf515d8a57e87f69190ba9b3703d25319c 100644
--- a/ash/common/system/chromeos/session/logout_button_tray.cc
+++ b/ash/common/system/chromeos/session/logout_button_tray.cc
@@ -9,7 +9,7 @@
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/system/chromeos/session/logout_confirmation_controller.h"
-#include "ash/common/system/tray/system_tray_delegate.h"
+#include "ash/common/system/tray/system_tray_controller.h"
 #include "ash/common/system/tray/system_tray_notifier.h"
 #include "ash/common/system/tray/tray_constants.h"
 #include "ash/common/system/tray/tray_utils.h"
@@ -155,7 +155,7 @@ void LogoutButtonTray::ButtonPressed(views::Button* sender,
 
   if (dialog_duration_ <= base::TimeDelta()) {
     // Sign out immediately if |dialog_duration_| is non-positive.
-    WmShell::Get()->system_tray_delegate()->SignOut();
+    WmShell::Get()->system_tray_controller()->SignOut();
   } else if (WmShell::Get()->logout_confirmation_controller()) {
     WmShell::Get()->logout_confirmation_controller()->ConfirmLogout(
         base::TimeTicks::Now() + dialog_duration_);