Add TrayLocale for locale change notifications.

ash/system/locale/locale_observer.h

+// Copyright (c) 2012 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 ASH_SYSTEM_LOCALE_LOCALE_OBSERVER_H_
+#define ASH_SYSTEM_LOCALE_LOCALE_OBSERVER_H_
+#pragma once
+
+#include "ash/ash_export.h"
+
+namespace ash {
+
+class ASH_EXPORT LocaleObserver {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    virtual void AcceptLocaleChange() = 0;
+    virtual void RevertLocaleChange() = 0;
+  };
+
+  virtual ~LocaleObserver() {}
+
+  virtual void OnLocaleChanged(Delegate* delegate,
+                               const std::string& cur_locale,
+                               const std::string& from_locale,
+                               const std::string& to_locale) = 0;
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_LOCALE_LOCALE_OBSERVER_H_