Mojo Example that demos the difference between providing and requesting an interface

examples/indirect_service/indirect_service_demo.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.
 
 module mojo.examples;
 
-interface EchoService {
-  EchoString(string? value) => (string? value);
+interface IntegerService {
+  Increment() => (int32 value);
 };
+
+interface IndirectIntegerService {
+  Set(IntegerService? service);
+  Get(IntegerService&? service);
+};