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

ios/web/webui/url_fetcher_block_adapter.mm

 // Copyright 2015 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/url_fetcher_block_adapter.h"
 
 #include "base/logging.h"
 #include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_request_context_getter.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 URLFetcherBlockAdapter::URLFetcherBlockAdapter(
     const GURL& url,
     net::URLRequestContextGetter* request_context,
     web::URLFetcherBlockAdapterCompletion completion_handler)
     : url_(url),
       request_context_(request_context),
       completion_handler_([completion_handler copy]) {
 }
@@ skipping 11 matching lines @@
   std::string response;
   if (!source->GetResponseAsString(&response)) {
     DLOG(WARNING) << "String for resource URL not found" << source->GetURL();
   }
   NSData* data =
       [NSData dataWithBytes:response.c_str() length:response.length()];
   completion_handler_.get()(data, this);
 }
 
 }  // namespace web