Simplify ArcServiceManager by stop deriving it from ArcIntentHelperObserver

components/arc/intent_helper/arc_intent_helper_observer.h

 // 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.
 
 #ifndef COMPONENTS_ARC_INTENT_HELPER_ARC_INTENT_HELPER_OBSERVER_H_
 #define COMPONENTS_ARC_INTENT_HELPER_ARC_INTENT_HELPER_OBSERVER_H_
 
 namespace arc {
 
 class ArcIntentHelperObserver {
  public:
   // Called when app's intent filter is updated.
   virtual void OnAppsUpdated() = 0;
-
- protected:
   virtual ~ArcIntentHelperObserver() = default;
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_INTENT_HELPER_ARC_INTENT_HELPER_OBSERVER_H_