Add shutdown notification and service refs to SyncServiceObserver.

ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.h

 // Copyright 2017 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 IOS_CHROME_BROWSER_SIGNIN_DESKTOP_PROMOTION_SYNC_OBSERVER_H_
 #define IOS_CHROME_BROWSER_SIGNIN_DESKTOP_PROMOTION_SYNC_OBSERVER_H_
 
 #include "base/macros.h"
 #include "components/sync/driver/sync_service_observer.h"
 
 namespace browser_sync {
 class ProfileSyncService;
 }
 
 class PrefService;
 
 // This class will implement ProfileSyncServiceObserver and will attach it self
 // to the sync service to observe the sync state change.
 // Once the sync state is changed and priority prefs are synced, the observer
 // will check the desktop promotion prefs, and if eligilble it will log desktop
 // promotion metrics to uma and mark the promotion cycle as completed in a perf.
 class DesktopPromotionSyncObserver : public syncer::SyncServiceObserver {
  public:
   DesktopPromotionSyncObserver(PrefService* pref_service,
                                browser_sync::ProfileSyncService* sync_service);
 
   ~DesktopPromotionSyncObserver() override;
 
   // ProfileSyncServiceObserver implementation.
-  void OnStateChanged() override;
+  void OnStateChanged(syncer::SyncService* sync) override;
 
  private:
   PrefService* pref_service_;
   browser_sync::ProfileSyncService* sync_service_;
   bool desktop_metrics_logger_initiated_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopPromotionSyncObserver);
 };
 
 #endif  // IOS_CHROME_BROWSER_SIGNIN_DESKTOP_PROMOTION_SYNC_OBSERVER_H_