[ARC] [Split this CL] Convert ios/web/webui to ARC.

ios/web/webui/web_ui_ios_impl.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/webui/web_ui_ios_impl.h"
 
 #include <stddef.h>
 
 #include "base/json/json_writer.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "ios/web/public/webui/web_ui_ios_controller.h"
 #include "ios/web/public/webui/web_ui_ios_controller_factory.h"
 #include "ios/web/public/webui/web_ui_ios_message_handler.h"
 #include "ios/web/web_state/web_state_impl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using web::WebUIIOSController;
 
 namespace web {
 
 // static
 base::string16 WebUIIOS::GetJavascriptCall(
     const std::string& function_name,
     const std::vector<const base::Value*>& arg_list) {
   base::string16 parameters;
   std::string json;
@@ skipping 116 matching lines @@
   handler->set_web_ui(this);
   handler->RegisterMessages();
   handlers_.push_back(handler);
 }
 
 void WebUIIOSImpl::ExecuteJavascript(const base::string16& javascript) {
   web_state_->ExecuteJavaScript(javascript);
 }
 
 }  // namespace web