Reland: chromeos: Convert ash VPNDelegate interface to mojo

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/ime_info.h"
 #include "ash/common/system/tray/system_tray_item.h"
 
 namespace ash {
@@ skipping 140 matching lines @@
 bool SystemTrayDelegate::IsSearchKeyMappedToCapsLock() {
   return false;
 }
 
 void SystemTrayDelegate::AddCustodianInfoTrayObserver(
     CustodianInfoTrayObserver* observer) {}
 
 void SystemTrayDelegate::RemoveCustodianInfoTrayObserver(
     CustodianInfoTrayObserver* observer) {}
 
-VPNDelegate* SystemTrayDelegate::GetVPNDelegate() const {
-  return nullptr;
-}
-
 std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateRotationLockTrayItem(
     SystemTray* tray) {
   return nullptr;
 }
 
 }  // namespace ash