media: add ArcCamera3Service Mojo service

media/capture/video/chromeos/mojo/arc_camera3_service.mojom

+// 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.
+
+module arc.mojom;
+
+import "arc_camera3.mojom";
+
+interface ArcCamera3Service {
+  RegisterCameraHal@0(ArcCamera3Hal camera_hal);
+
+  RegisterClient@1(ArcCamera3Client client);
+};
+
+interface ArcCamera3Hal {
+  OpenCameraHal@0(CameraModule& camera_module);
+};
+
+interface ArcCamera3Client {
+  NotifyCameraHalRegistered@0(CameraModule camera_module);
+};