Service Manager: Implement graceful service termination

services/service_manager/public/interfaces/service_control.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 service_manager.mojom;
+
+// The client interface a Service uses to issue requests to the Service Manager.
+interface ServiceControl {
+  // Informs the Service Manager that the Service is ready to terminate. If
+  // the Service Manager needs the Service to stay alive - for example, if
+  // there's an in-flight OnConnect request which hasn't been acked yet - this
+  // request is ignored. Otherwise the Service pipe will soon be severed by
+  // the Service Manager, signaling that shutdown may proceed at the service's
+  // own discretion.
+  RequestQuit();
+};