Neuter the wrong-way ServiceProvider (a.k.a. exposed_services).

mojo/public/interfaces/application/shell.mojom

 // Copyright 2014 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.
 
 [DartPackage="mojo"]
 module mojo;
 
 import "mojo/public/interfaces/application/application_connector.mojom";
 import "mojo/public/interfaces/application/service_provider.mojom";
 
 // An interface through which a Mojo application may communicate with the Mojo
 // system and request connections to other applications.
 interface Shell {
   // See |ApplicationConnector.ConnectToApplication()|.
-  // TODO(vtl): Maybe this should be deprecated/removed.
+  //
+  // WARNING: |exposed_services| is deprecated and non-functional, and will be
+  // removed. Note that this also means that |services| will become required.
+  // https://github.com/domokit/mojo/issues/762
+  //
+  // TODO(vtl): Maybe this should be deprecated/removed (in favor of just using
+  // |ApplicationConnector|).
   ConnectToApplication(string application_url,
                        ServiceProvider&? services,
                        ServiceProvider? exposed_services);
 
   CreateApplicationConnector(
       ApplicationConnector& application_connector_request);
 };