Replace base::CallbackList with base::ObserverList in CastConfigDelegate

chrome/browser/ui/ash/cast_config_delegate_chromeos.h

 // Copyright 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_UI_ASH_CAST_CONFIG_DELEGATE_CHROMEOS_H_
 #define CHROME_BROWSER_UI_ASH_CAST_CONFIG_DELEGATE_CHROMEOS_H_
 
 #include <string>
 
 #include "ash/cast_config_delegate.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/values.h"
 
 namespace chromeos {
 
 // A class which allows the ash tray to communicate with the cast extension.
 class CastConfigDelegateChromeos : public ash::CastConfigDelegate {
  public:
   CastConfigDelegateChromeos();
   ~CastConfigDelegateChromeos() override;
 
  private:
   // CastConfigDelegate:
   bool HasCastExtension() const override;
-  DeviceUpdateSubscription RegisterDeviceUpdateObserver(
-      const ReceiversAndActivitesCallback& callback) override;
   void RequestDeviceRefresh() override;
   void CastToReceiver(const std::string& receiver_id) override;
   void StopCasting(const std::string& activity_id) override;
   bool HasOptions() const override;
   void LaunchCastOptions() override;
+  void AddObserver(ash::CastConfigDelegate::Observer* observer) override;
+  void RemoveObserver(ash::CastConfigDelegate::Observer* observer) override;
 
   DISALLOW_COPY_AND_ASSIGN(CastConfigDelegateChromeos);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_ASH_CAST_CONFIG_DELEGATE_CHROMEOS_H_