Convert //ios from scoped_ptr to std::unique_ptr.

ios/chrome/browser/signin/account_tracker_service_factory.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 IOS_CHROME_BROWSER_SIGNIN_ACCOUNT_TRACKER_SERVICE_FACTORY_H_
 #define IOS_CHROME_BROWSER_SIGNIN_ACCOUNT_TRACKER_SERVICE_FACTORY_H_
 
+#include <memory>
+
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
 class AccountTrackerService;
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
 }  // namespace base
 
 namespace ios {
@@ skipping 16 matching lines @@
 
  private:
   friend struct base::DefaultSingletonTraits<AccountTrackerServiceFactory>;
 
   AccountTrackerServiceFactory();
   ~AccountTrackerServiceFactory() override;
 
   // BrowserStateKeyedServiceFactory implementation.
   void RegisterBrowserStatePrefs(
       user_prefs::PrefRegistrySyncable* registry) override;
-  scoped_ptr<KeyedService> BuildServiceInstanceFor(
+  std::unique_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(AccountTrackerServiceFactory);
 };
 
 }  // namespace ios
 
 #endif  // IOS_CHROME_BROWSER_SIGNIN_ACCOUNT_TRACKER_SERVICE_FACTORY_H_