Use mojo SystemTray interfaces for both mash and classic ash

chrome/browser/ui/ash/system_tray_common.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_COMMON_H_
 #define CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_COMMON_H_
 
 #include <string>
 
 #include "base/macros.h"
 
 // System tray code shared between classic ash SystemTrayDelegateChromeos and
 // mustash SystemTrayClient.
+// TODO: all this code moves directly in SystemTrayClient. Less indirection.
 class SystemTrayCommon {
  public:
   static const char kDisplaySettingsSubPageName[];
   static const char kDisplayOverscanSettingsSubPageName[];
 
   // Shows general settings UI.
   static void ShowSettings();
 
-  // Shows the settings related to date, timezone etc.
-  static void ShowDateSettings();
-
   // Shows settings related to multiple displays.
   static void ShowDisplaySettings();
 
   // Shows the page that lets you disable performance tracing.
   static void ShowChromeSlow();
 
   // Shows settings related to input methods.
   static void ShowIMESettings();
 
   // Shows help.
@@ skipping 15 matching lines @@
   static void ShowPublicAccountInfo();
 
   // Shows UI for changing proxy settings.
   static void ShowProxySettings();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(SystemTrayCommon);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_COMMON_H_