arc: Show custom notification via notification surface

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 f75b8286b7e1a07f6f585a8547e595394e29a3e1..ba53b9602835d09cf05cd6a72aeb502ace7f918a 100644
--- a/ui/arc/notification/arc_notification_manager.h
+++ b/ui/arc/notification/arc_notification_manager.h
@@ -5,6 +5,7 @@
 #ifndef UI_ARC_NOTIFICATION_ARC_NOTIFICATION_MANAGER_H_
 #define UI_ARC_NOTIFICATION_ARC_NOTIFICATION_MANAGER_H_
 
+#include <memory>
 #include <string>
 #include <unordered_map>
 
@@ -18,6 +19,7 @@
 namespace arc {
 
 class ArcNotificationItem;
+class ArcNotificationSurfaceCollection;
 
 class ArcNotificationManager : public ArcService,
                                public ArcBridgeService::Observer,
@@ -48,6 +50,10 @@ class ArcNotificationManager : public ArcService,
   void SendNotificationButtonClickedOnChrome(
       const std::string& key, int button_index);
 
+  ArcNotificationSurfaceCollection* notification_surface_collection() {
+    return notification_surface_collection_.get();
+  }
+
  private:
   const AccountId main_profile_id_;
   message_center::MessageCenter* const message_center_;
@@ -58,6 +64,9 @@ class ArcNotificationManager : public ArcService,
 
   bool ready_ = false;
 
+  std::unique_ptr<ArcNotificationSurfaceCollection>
+      notification_surface_collection_;
+
   mojo::Binding<arc::mojom::NotificationsHost> binding_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcNotificationManager);