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 {
+
+// 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:
+  ArcService() {}
+  virtual ~ArcService() {}
+

[elijahtaylor1, 2016/01/20 00:41:19]

all of the children of ArcService hold a weak reference to ArcBridgeService. 
Can that be part of this class instead along with the calls to add/remove
observers?  Or maybe adding the service to the service manager can add the
observer?

[Luis Héctor Chávez, 2016/01/20 17:39:59]

Made this own the ArcBridgeService*.

+ private:
+  DISALLOW_COPY_AND_ASSIGN(ArcService);
+};
+
+}  // namespace arc
+
+#endif  // COMPONENTS_ARC_ARC_SERVICE_H_