mash: Create system tray display and rotation lock items via delegate

ash/common/system/tray/system_tray_delegate.cc

 // 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.
 
 #include "ash/common/system/tray/system_tray_delegate.h"
 
+#include "ash/common/system/tray/system_tray_item.h"
+
 namespace ash {
 
 NetworkIconInfo::NetworkIconInfo()
     : connecting(false),
       connected(false),
       tray_icon_visible(true),
       is_cellular(false) {}
 
 NetworkIconInfo::~NetworkIconInfo() {}
 
@@ skipping 210 matching lines @@
 void SystemTrayDelegate::RemoveShutdownPolicyObserver(
     ShutdownPolicyObserver* observer) {}
 
 void SystemTrayDelegate::ShouldRebootOnShutdown(
     const RebootOnShutdownCallback& callback) {}
 
 VPNDelegate* SystemTrayDelegate::GetVPNDelegate() const {
   return nullptr;
 }
 
+std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateDisplayTrayItem(
+    SystemTray* tray) {
+  return nullptr;
+}
+
+std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateRotationLockTrayItem(
+    SystemTray* tray) {
+  return nullptr;
+}
+
 }  // namespace ash