[Mojo Video Capture] Stop service when last client disconnects.

services/video_capture/public/cpp/BUILD.gn

+# Copyright 2017 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.
+
+source_set("cpp") {
+  sources = [
+    "device_to_feedback_observer_adapter.cc",
+    "device_to_feedback_observer_adapter.h",
+    "receiver_media_to_mojo_adapter.cc",
+    "receiver_media_to_mojo_adapter.h",
+  ]
+
+  public_deps = [
+    "//base",
+    "//media",
+    "//media/capture:capture",
+    "//services/service_manager/public/cpp",
+    "//services/video_capture/public/interfaces",
+  ]
+
+  deps = [
+    "//mojo/public/cpp/bindings:bindings",
+  ]
+}