Simplify ArcServiceManager by stop deriving it from ArcIntentHelperObserver

chrome/browser/chromeos/arc/arc_service_launcher.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 "chrome/browser/chromeos/arc/arc_service_launcher.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 83 matching lines @@
       base::MakeUnique<ArcContentFileSystemService>(arc_bridge_service));
   arc_service_manager_->AddService(base::MakeUnique<ArcCrashCollectorBridge>(
       arc_bridge_service, arc_service_manager_->blocking_task_runner()));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcDownloadsWatcherService>(arc_bridge_service));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcEnterpriseReportingService>(arc_bridge_service));
   auto intent_helper = base::MakeUnique<ArcIntentHelperBridge>(
       arc_bridge_service, arc_service_manager_->icon_loader(),
       arc_service_manager_->activity_resolver());
-  // We don't have to remove observer since
-  // ArcServiceManager always outlives ArcIntentHelperBridge.
-  intent_helper->AddObserver(arc_service_manager_.get());
+  // We don't have to call ArcIntentHelperBridge::RemoveObserver() in
+  // ~ArcServiceManager() since the observer in ArcServiceManager always
+  // outlives the ArcIntentHelperBridge object.
+  intent_helper->AddObserver(arc_service_manager_->intent_helper_observer());
   arc_service_manager_->AddService(std::move(intent_helper));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcImeService>(arc_bridge_service));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcKioskBridge>(arc_bridge_service));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcMetricsService>(arc_bridge_service));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcNetHostImpl>(arc_bridge_service));
   arc_service_manager_->AddService(
@@ skipping 28 matching lines @@
 
 void ArcServiceLauncher::Shutdown() {
   DCHECK(arc_service_manager_);
   // Destroy in the reverse order of the initialization.
   arc_service_manager_->Shutdown();
   arc_session_manager_.reset();
   arc_service_manager_.reset();
 }
 
 }  // namespace arc