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

ash/mus/system_tray_delegate_mus.cc

+// 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.
+
+#include "ash/mus/system_tray_delegate_mus.h"
+
+#include "ash/common/system/tray/system_tray_notifier.h"
+#include "ash/common/wm_shell.h"
+#include "base/i18n/time_formatting.h"
+
+namespace ash {
+
+SystemTrayDelegateMus::SystemTrayDelegateMus()
+    : hour_clock_type_(base::GetHourClockType()) {}
+
+SystemTrayDelegateMus::~SystemTrayDelegateMus() {}
+
+base::HourClockType SystemTrayDelegateMus::GetHourClockType() const {
+  return hour_clock_type_;
+}
+
+void SystemTrayDelegateMus::SetUse24HourClock(bool use_24_hour) {
+  hour_clock_type_ = use_24_hour ? base::k24HourClock : base::k12HourClock;
+  WmShell::Get()->system_tray_notifier()->NotifyDateFormatChanged();
+}
+
+}  // namespace ash