[ObjC ARC] Converts ios/net to ARC.

ios/net/cookies/system_cookie_util.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/net/cookies/system_cookie_util.h"
 
 #import <Foundation/Foundation.h>
 #include <stddef.h>
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "net/cookies/cookie_constants.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace net {
 
 namespace {
 
 // Used to report cookie loss events in UMA.
 enum CookieLossType {
   LOSS,
   NOT_ENOUGH_COOKIES,  // Not enough cookies, error checking is disabled.
   NO_LOSS,
   COOKIE_LOSS_ENUM_COUNT
@@ skipping 120 matching lines @@
   ResetCookieCountMetrics();
 }
 
 void ResetCookieCountMetrics() {
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   [defaults setBool:NO forKey:kCheckCookieLossKey];
   [defaults synchronize];
 }
 
 }  // namespace net