arc-bridge: Introduce the ArcService class

components/arc/arc_service.h

+// 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.
+
+#ifndef COMPONENTS_ARC_ARC_SERVICE_H_
+#define COMPONENTS_ARC_ARC_SERVICE_H_
+
+#include "base/macros.h"
+
+namespace arc {
+
+class ArcBridgeService;
+
+// Abstract class whose lifecycle will be managed by the ArcServiceManager.  It
+// is guaranteed that once the ownership of an ArcService has been transferred
+// to ArcServiceManager, it will outlive the ArcBridgeService, so it is safe to
+// keep a weak reference to it.
+class ArcService {
+ public:
+  virtual ~ArcService();
+
+  ArcBridgeService* arc_bridge_service() const { return arc_bridge_service_; }
+
+ protected:
+  explicit ArcService(ArcBridgeService* arc_bridge_service);
+
+ private:
+  ArcBridgeService* const arc_bridge_service_;  // owned by ArcServiceManager.
+
+  DISALLOW_COPY_AND_ASSIGN(ArcService);
+};
+
+}  // namespace arc
+
+#endif  // COMPONENTS_ARC_ARC_SERVICE_H_