mash: Fix system tray clock 12/24 hour time setting

chrome/browser/ui/ash/system_tray_controller_mus.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_CONTROLLER_MUS_H_
+#define CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_CONTROLLER_MUS_H_
+
+#include "ash/public/interfaces/system_tray.mojom.h"
+#include "base/macros.h"
+#include "chrome/browser/chromeos/system/system_clock_observer.h"
+
+// Controls chrome's interaction with the ash system tray menu.
+class SystemTrayControllerMus : public chromeos::system::SystemClockObserver {
+ public:
+  SystemTrayControllerMus();
+  ~SystemTrayControllerMus() override;
+
+ private:
+  // chromeos::system::SystemClockObserver:
+  void OnSystemClockChanged(chromeos::system::SystemClock* clock) override;
+
+  ash::mojom::SystemTrayPtr system_tray_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemTrayControllerMus);
+};
+
+#endif  // CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_CONTROLLER_MUS_H_