Enable strict-virtual-specifiers for iOS builds.

ios/chrome/browser/suggestions/suggestions_service_factory.h

 // Copyright 2014 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_SUGGESTIONS_SUGGESTIONS_SERVICE_FACTORY_H_
 #define IOS_CHROME_BROWSER_SUGGESTIONS_SUGGESTIONS_SERVICE_FACTORY_H_
 
 #include "base/macros.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
@@ skipping 15 matching lines @@
   static SuggestionsServiceFactory* GetInstance();
 
   // Returns the SuggestionsService for |browser_state|.
   static SuggestionsService* GetForBrowserState(
       web::BrowserState* browser_state);
 
  private:
   friend struct DefaultSingletonTraits<SuggestionsServiceFactory>;
 
   SuggestionsServiceFactory();
-  ~SuggestionsServiceFactory();
+  ~SuggestionsServiceFactory() override;
 
   // BrowserStateKeyedServiceFactory:
   KeyedService* BuildServiceInstanceFor(
       web::BrowserState* browser_state) const override;
   void RegisterProfilePrefs(
       user_prefs::PrefRegistrySyncable* registry) override;
 
   DISALLOW_COPY_AND_ASSIGN(SuggestionsServiceFactory);
 };
 
 }  // namespace suggestions
 
 #endif  // IOS_CHROME_BROWSER_SUGGESTIONS_SUGGESTIONS_SERVICE_FACTORY_H_