arc: Revamp the ArcBridgeService interface

chrome/browser/chromeos/arc/arc_settings_service.h

 // Copyright (c) 2015 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 CHROME_BROWSER_CHROMEOS_ARC_ARC_SETTINGS_SERVICE_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_SETTINGS_SERVICE_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "components/arc/arc_bridge_service.h"
 #include "components/arc/arc_service.h"
+#include "components/arc/instance_holder.h"
 
 namespace arc {
 
 class ArcSettingsServiceImpl;
 
-class ArcSettingsService : public ArcService,
-                           public ArcBridgeService::Observer {
+class ArcSettingsService
+    : public ArcService,
+      public InstanceHolder<mojom::IntentHelperInstance>::Observer {
  public:
   explicit ArcSettingsService(ArcBridgeService* bridge_service);
   ~ArcSettingsService() override;
 
-  // ArcBridgeService::Observer
-  void OnIntentHelperInstanceReady() override;
-  void OnIntentHelperInstanceClosed() override;
+  // InstanceHolder<mojom::IntentHelperInstance>::Observer
+  void OnInstanceReady() override;
+  void OnInstanceClosed() override;
 
  private:
   std::unique_ptr<ArcSettingsServiceImpl> impl_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcSettingsService);
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_SETTINGS_SERVICE_H_