chromeos: Move ownership of ash VPN provider list from chrome into ash

ash/mus/vpn_delegate_mus.cc

 // 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.
 
 #include "ash/mus/vpn_delegate_mus.h"
 
 namespace ash {
 
 VPNDelegateMus::VPNDelegateMus() {}
 
 VPNDelegateMus::~VPNDelegateMus() {}
 
-bool VPNDelegateMus::HaveThirdPartyVPNProviders() const {
-  // TODO(mash): http://crbug.com/651148
-  return false;
-}
-
-const std::vector<VPNProvider>& VPNDelegateMus::GetVPNProviders() const {
-  // TODO(mash): http://crbug.com/651148
-  return providers_;
-}
-
-void VPNDelegateMus::ShowAddPage(const VPNProvider::Key& key) {
+void VPNDelegateMus::ShowAddPage(const std::string& extension_id) {
   // TODO(mash): http://crbug.com/651148
 }
 
 }  // namespace ash