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

ios/web/public/test/http_server/error_page_response_provider.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.
 
 #import "ios/web/public/test/http_server/error_page_response_provider.h"
 
 #include "base/logging.h"
 #import "ios/web/public/test/http_server/http_server.h"
 #include "net/http/http_status_code.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // static
 GURL ErrorPageResponseProvider::GetDnsFailureUrl() {
   return GURL("http://mock/bad");
 }
 
 // static
 GURL ErrorPageResponseProvider::GetRedirectToDnsFailureUrl() {
   return web::test::HttpServer::MakeUrl("http://mock/redirect");
 }
 
@@ skipping 11 matching lines @@
   if (HtmlResponseProvider::CanHandleRequest(request)) {
     HtmlResponseProvider::GetResponseHeadersAndBody(request, headers,
                                                     response_body);
   } else if (request.url == GetRedirectToDnsFailureUrl()) {
     *headers = web::ResponseProvider::GetRedirectResponseHeaders(
         ErrorPageResponseProvider::GetDnsFailureUrl().spec(), net::HTTP_FOUND);
   } else {
     NOTREACHED();
   }
 }