arc-bridge: Introduce the ArcService class

ui/arc/notification/arc_notification_manager.h

Index: ui/arc/notification/arc_notification_manager.h
diff --git a/ui/arc/notification/arc_notification_manager.h b/ui/arc/notification/arc_notification_manager.h
index d197be81e4b643bea1ec9c52f12683b17fc85938..94f270c16522fe57a5d9b545aee975bbb8ada1eb 100644
--- a/ui/arc/notification/arc_notification_manager.h
+++ b/ui/arc/notification/arc_notification_manager.h
@@ -10,6 +10,7 @@
 
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "components/arc/arc_bridge_service.h"
+#include "components/arc/arc_service.h"
 #include "components/arc/common/notifications.mojom.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "mojo/public/cpp/bindings/binding.h"
@@ -18,10 +19,11 @@ namespace arc {
 
 class ArcNotificationItem;
 
-class ArcNotificationManager : public ArcBridgeService::Observer,
+class ArcNotificationManager : public ArcService,
+                               public ArcBridgeService::Observer,
                                public NotificationsHost {
  public:
-  ArcNotificationManager(ArcBridgeService* bridge_service,
+  ArcNotificationManager(ArcBridgeService* arc_bridge,
                          const AccountId& main_profile_id);
   ~ArcNotificationManager() override;
 
@@ -37,7 +39,7 @@ class ArcNotificationManager : public ArcBridgeService::Observer,
   void SendNotificationClickedOnChrome(const std::string& key);
 
  private:
-  ArcBridgeService* const arc_bridge_;
+  ArcBridgeService* const arc_bridge_service_;  // owned by ArcServiceManager.
   const AccountId main_profile_id_;
 
   using ItemMap =