chromeos: Migrate SignOut and RequestRestartForUpdate to mojo interface

ash/common/test/test_system_tray_delegate.cc

Index: ash/common/test/test_system_tray_delegate.cc
diff --git a/ash/common/test/test_system_tray_delegate.cc b/ash/common/test/test_system_tray_delegate.cc
index 9e4bf2c3a917e45d904fc0b8316de95399d4c5d7..8ce4a759060d3964d815facf50d20abc35d6a88e 100644
--- a/ash/common/test/test_system_tray_delegate.cc
+++ b/ash/common/test/test_system_tray_delegate.cc
@@ -9,7 +9,6 @@
 #include "ash/common/login_status.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/wm_shell.h"
-#include "base/message_loop/message_loop.h"
 #include "base/time/time.h"
 
 namespace ash {
@@ -100,10 +99,6 @@ bool TestSystemTrayDelegate::GetSessionLengthLimit(
   return session_length_limit_set_;
 }
 
-void TestSystemTrayDelegate::SignOut() {
-  base::MessageLoop::current()->QuitWhenIdle();
-}
-
 void TestSystemTrayDelegate::GetCurrentIME(IMEInfo* info) {
   *info = current_ime_;
 }