Switch from Delegate to Observer.

ui/arc/notification/arc_notification_manager_unittest.cc

 // 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.
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "components/arc/instance_holder.h"
-#include "components/arc/test/fake_arc_bridge_instance.h"
 #include "components/arc/test/fake_arc_bridge_service.h"
 #include "components/arc/test/fake_notifications_instance.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/arc/notification/arc_notification_manager.h"
 #include "ui/message_center/fake_message_center.h"
 
 namespace arc {
 
 namespace {
 
@@ skipping 154 matching lines @@
   CreateNotificationWithKey("notification2");
   CreateNotificationWithKey("notification3");
   EXPECT_EQ(3u, message_center()->GetVisibleNotifications().size());
 
   arc_notification_manager()->OnInstanceClosed();
 
   EXPECT_EQ(0u, message_center()->GetVisibleNotifications().size());
 }
 
 }  // namespace arc