[ObjC ARC] Converts ios/chrome/browser/browser_state to ARC.

ios/chrome/browser/browser_state/chrome_browser_state.mm

 // 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.
 
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 
 #include <utility>
 
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/sequenced_task_runner.h"
 #include "components/prefs/json_pref_store.h"
 #include "components/sync_preferences/pref_service_syncable.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #include "ios/chrome/browser/net/ios_chrome_url_request_context_getter.h"
 #include "ios/chrome/browser/net/net_types.h"
 #include "ios/web/public/web_state/web_state.h"
 #include "ios/web/public/web_thread.h"
 #include "ios/web/public/webui/web_ui_ios.h"
 #include "ios/web/webui/url_data_manager_ios_backend.h"
 #include "net/url_request/url_request_interceptor.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace ios {
 
 ChromeBrowserState::ChromeBrowserState() {}
 
 ChromeBrowserState::~ChromeBrowserState() {}
 
 // static
 ChromeBrowserState* ChromeBrowserState::FromBrowserState(
     web::BrowserState* browser_state) {
   // This is safe; this is the only implementation of BrowserState.
@@ skipping 40 matching lines @@
             web::URLDataManagerIOSBackend::CreateProtocolHandler(this)
                 .release());
     URLRequestInterceptorScopedVector request_interceptors;
     request_context_getter_ = make_scoped_refptr(CreateRequestContext(
         &protocol_handlers, std::move(request_interceptors)));
   }
   return request_context_getter_.get();
 }
 
 }  // namespace ios