Reland: chromeos: Convert ash VPNDelegate interface to mojo

ash/public/interfaces/vpn_list.mojom

Index: ash/public/interfaces/vpn_list.mojom
diff --git a/ash/public/interfaces/vpn_list.mojom b/ash/public/interfaces/vpn_list.mojom
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+// 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 client interface (usually provided by chrome browser).
+  SetClient(VpnListClient client);
+
+  // 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);
+};
+
+// Allows ash to make requests of chrome browser, e.g. to show webui settings.
+interface VpnListClient {
+  // Shows the configuration page for the built-in OpenVPN / L2TP provider.
+  ShowBuiltInAddNetworkPage();
+
+  // Shows the configuration page for a third-party VPN. |extension_id| must be
+  // a valid, non-empty extension ID.
+  ShowThirdPartyAddNetworkPage(string extension_id);
+};