Convert ios_web_shell to ARC.

ios/web/shell/shell_url_request_context_getter.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/web/shell/shell_url_request_context_getter.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/base_paths.h"
@@ skipping 20 matching lines @@
 #include "net/proxy/proxy_service.h"
 #include "net/ssl/channel_id_service.h"
 #include "net/ssl/default_channel_id_store.h"
 #include "net/ssl/ssl_config_service_defaults.h"
 #include "net/url_request/data_protocol_handler.h"
 #include "net/url_request/static_http_user_agent_settings.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_storage.h"
 #include "net/url_request/url_request_job_factory_impl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 ShellURLRequestContextGetter::ShellURLRequestContextGetter(
     const base::FilePath& base_path,
     const scoped_refptr<base::SingleThreadTaskRunner>& network_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& file_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& cache_task_runner)
     : base_path_(base_path),
       file_task_runner_(file_task_runner),
       network_task_runner_(network_task_runner),
@@ skipping 103 matching lines @@
 
   return url_request_context_.get();
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 ShellURLRequestContextGetter::GetNetworkTaskRunner() const {
   return network_task_runner_;
 }
 
 }  // namespace web