arc-bridge: Introduce the ArcService class

ui/arc/notification/arc_notification_manager.cc

Index: ui/arc/notification/arc_notification_manager.cc
diff --git a/ui/arc/notification/arc_notification_manager.cc b/ui/arc/notification/arc_notification_manager.cc
index 91b8c269b2517fc2bced797f96c0d924b6744f94..5a1ccb94013e65ba998d8895a8a9ac632d1a38f4 100644
--- a/ui/arc/notification/arc_notification_manager.cc
+++ b/ui/arc/notification/arc_notification_manager.cc
@@ -14,16 +14,17 @@ ArcNotificationManager::ArcNotificationManager(ArcBridgeService* arc_bridge,
     : arc_bridge_(arc_bridge),
       main_profile_id_(main_profile_id),
       binding_(this) {
-  // This must be initialized after ArcBridgeService.
   DCHECK(arc_bridge_);
-  DCHECK_EQ(arc_bridge_, ArcBridgeService::Get());
   arc_bridge_->AddObserver(this);
+
+  // If NotificationsInstance was ready before we AddObserver(), we won't get
+  // OnNotificationsInstanceReady events. For such case, we have to call it
+  // explicitly.
+  if (arc_bridge_->notifications_instance())
+    OnNotificationsInstanceReady();
 }
 
 ArcNotificationManager::~ArcNotificationManager() {
-  // This should be free'd before ArcBridgeService.
-  DCHECK(ArcBridgeService::Get());
-  DCHECK_EQ(arc_bridge_, ArcBridgeService::Get());
   arc_bridge_->RemoveObserver(this);
 }