[ObjC ARC] Converts ios/chrome/browser/signin:signin to ARC.

ios/chrome/browser/signin/oauth2_token_service_factory.mm

 // 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.
 
 #include "ios/chrome/browser/signin/oauth2_token_service_factory.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
 #include "components/signin/core/common/signin_pref_names.h"
 #include "components/signin/ios/browser/profile_oauth2_token_service_ios_delegate.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/signin/account_tracker_service_factory.h"
 #include "ios/chrome/browser/signin/profile_oauth2_token_service_ios_provider_impl.h"
 #include "ios/chrome/browser/signin/signin_client_factory.h"
 #include "ios/chrome/browser/signin/signin_error_controller_factory.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 OAuth2TokenServiceFactory::OAuth2TokenServiceFactory()
     : BrowserStateKeyedServiceFactory(
           "ProfileOAuth2TokenService",
           BrowserStateDependencyManager::GetInstance()) {
   DependsOn(ios::AccountTrackerServiceFactory::GetInstance());
   DependsOn(SigninClientFactory::GetInstance());
   DependsOn(ios::SigninErrorControllerFactory::GetInstance());
 }
 
 OAuth2TokenServiceFactory::~OAuth2TokenServiceFactory() {}
@@ skipping 23 matching lines @@
       ios::ChromeBrowserState::FromBrowserState(context);
   auto delegate = base::MakeUnique<ProfileOAuth2TokenServiceIOSDelegate>(
       SigninClientFactory::GetForBrowserState(chrome_browser_state),
       base::MakeUnique<ProfileOAuth2TokenServiceIOSProviderImpl>(),
       ios::AccountTrackerServiceFactory::GetForBrowserState(
           chrome_browser_state),
       ios::SigninErrorControllerFactory::GetForBrowserState(
           chrome_browser_state));
   return base::MakeUnique<ProfileOAuth2TokenService>(std::move(delegate));
 }