mash: Add SystemTrayClient interface, use to show date settings

ash/mus/system_tray_delegate_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 ASH_MUS_SYSTEM_TRAY_DELEGATE_MUS_H_
 #define ASH_MUS_SYSTEM_TRAY_DELEGATE_MUS_H_
 
 #include "ash/common/system/tray/default_system_tray_delegate.h"
 #include "ash/public/interfaces/system_tray.mojom.h"
 #include "base/i18n/time_formatting.h"
 #include "base/macros.h"
 
+namespace shell {
+class Connector;
+}
+
 namespace ash {
 
 // Handles the settings displayed in the system tray menu. For mus most settings
 // are obtained from chrome browser via mojo IPC. For the classic ash version
 // see SystemTrayDelegateChromeOS.
 //
 // TODO: Support all methods in SystemTrayDelegate. http://crbug.com/647412.
 class SystemTrayDelegateMus : public DefaultSystemTrayDelegate,
                               public mojom::SystemTray {
  public:
-  SystemTrayDelegateMus();
+  explicit SystemTrayDelegateMus(shell::Connector* connector);
   ~SystemTrayDelegateMus() override;
 
   static SystemTrayDelegateMus* Get();
 
  private:
+  // Connects or reconnects the |system_tray_client_| interface.
+  void ConnectToSystemTrayClient();
+
+  // Handles errors on the |system_tray_client_| interface connection.
+  void OnClientConnectionError();
+
   // SystemTrayDelegate:
   base::HourClockType GetHourClockType() const override;
+  void ShowDateSettings() override;
 
   // mojom::SystemTray:
   void SetUse24HourClock(bool use_24_hour) override;
 
+  // May be null in unit tests.
+  shell::Connector* connector_;
+
+  // Client interface in chrome browser.
+  mojom::SystemTrayClientPtr system_tray_client_;
+
   // 12 or 24 hour display.
   base::HourClockType hour_clock_type_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayDelegateMus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_MUS_SYSTEM_TRAY_DELEGATE_MUS_H_