Revert of chromeos: Convert ash VPNDelegate interface to mojo

ash/public/interfaces/vpn_list.mojom

-// 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.
-
-module ash.mojom;
-
-// Describes a third-party VPN provided by an extension (e.g. Cisco AnyConnect).
-struct ThirdPartyVpnProvider {
-  string name;
-  string extension_id;
-};
-
-// Manages the VPN provider list in ash. Allows extension-backed VPN providers
-// to be added. Ash handles the built-in OpenVPN / L2TP provider internally.
-interface VpnList {
-  // Sets the list of third-party VPN providers. The |providers| array may be
-  // empty to clear the list (e.g. after the last third-party VPN extension is
-  // uninstalled).
-  SetThirdPartyVpnProviders(array<ThirdPartyVpnProvider> providers);
-};