[ObjC ARC] Converts ios/chrome/browser/ui/ntp:ntp_internal to ARC.

ios/chrome/browser/ui/ntp/notification_promo_whats_new.mm

 // Copyright (c) 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.
 
 #import "ios/chrome/browser/ui/ntp/notification_promo_whats_new.h"
 
 #include <stdint.h>
 #include <algorithm>
 #include <memory>
 #include <vector>
 
 #include "base/json/json_reader.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
 #include "base/strings/string_util.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/prefs/pref_service.h"
 #include "ios/chrome/browser/experimental_flags.h"
 #include "ios/chrome/browser/notification_promo.h"
 #include "ios/chrome/browser/pref_names.h"
 #include "ios/chrome/browser/ui/commands/ios_command_ids.h"
 #include "ios/chrome/grit/ios_chromium_strings.h"
 #include "ios/chrome/grit/ios_strings.h"
 #include "ui/base/l10n/l10n_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 struct PromoStringToIdsMapEntry {
   const char* promo_text_str;
   int message_id;
 };
 
 // A mapping from a string to a l10n message id.
 const PromoStringToIdsMapEntry kPromoStringToIdsMap[] = {
     {"appRatingPromo", IDS_IOS_APP_RATING_PROMO_STRING},
@@ skipping 217 matching lines @@
   std::string promo_json_filled_in =
       base::ReplaceStringPlaceholders(promo_json, replacements, NULL);
 
   std::unique_ptr<base::Value> value(
       base::JSONReader::Read(promo_json_filled_in));
   base::DictionaryValue* dict = NULL;
   if (value->GetAsDictionary(&dict)) {
     notification_promo_.InitFromJson(*dict);
   }
 }