[ObjC ARC] Converts ios/web/public/test/http_server:http_server to ARC.

ios/web/public/test/http_server/http_server_util.mm

 // Copyright 2016 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/public/test/http_server/http_server_util.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/path_service.h"
 #import "ios/web/public/test/http_server/html_response_provider.h"
 #import "ios/web/public/test/http_server/http_server.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 namespace test {
 
 void SetUpSimpleHttpServer(const std::map<GURL, std::string>& responses) {
   SetUpHttpServer(base::MakeUnique<HtmlResponseProvider>(responses));
 }
 
 void SetUpSimpleHttpServerWithSetCookies(
     const std::map<GURL, std::pair<std::string, std::string>>& responses) {
   SetUpHttpServer(base::MakeUnique<HtmlResponseProvider>(responses));
@@ skipping 12 matching lines @@
 }
 
 void AddResponseProvider(std::unique_ptr<web::ResponseProvider> provider) {
   web::test::HttpServer& server = web::test::HttpServer::GetSharedInstance();
   DCHECK(server.IsRunning());
   server.AddResponseProvider(std::move(provider));
 }
 
 }  // namespace test
 }  // namespace web