mustash: Convert TraySupervisedUserTest to AshTest

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 a40c227789b65d66b6c76f8ba5b8b14b75730a27..9e4bf2c3a917e45d904fc0b8316de95399d4c5d7 100644
--- a/ash/common/test/test_system_tray_delegate.cc
+++ b/ash/common/test/test_system_tray_delegate.cc
@@ -28,11 +28,6 @@ TestSystemTrayDelegate::TestSystemTrayDelegate()
 TestSystemTrayDelegate::~TestSystemTrayDelegate() {}
 
 // static
-void TestSystemTrayDelegate::SetInitialLoginStatus(LoginStatus login_status) {
-  g_initial_status = login_status;
-}
-
-// static
 void TestSystemTrayDelegate::SetSystemUpdateRequired(bool required) {
   g_system_update_required = required;
 }
@@ -117,5 +112,16 @@ void TestSystemTrayDelegate::GetAvailableIMEList(IMEInfoList* list) {
   *list = ime_list_;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+
+ScopedInitialLoginStatus::ScopedInitialLoginStatus(LoginStatus new_status)
+    : old_status_(g_initial_status) {
+  g_initial_status = new_status;
+}
+
+ScopedInitialLoginStatus::~ScopedInitialLoginStatus() {
+  g_initial_status = old_status_;
+}
+
 }  // namespace test
 }  // namespace ash