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

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

 // Copyright (c) 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/chrome/browser/ui/ntp/notification_promo_whats_new.h"
 
 #include <map>
 
 #include "base/bind.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/user_metrics.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/variations/variations_associated_data.h"
 #include "ios/chrome/browser/ui/commands/ios_command_ids.h"
 #include "ios/chrome/grit/ios_chromium_strings.h"
 #include "ios/public/provider/chrome/browser/images/whats_new_icon.h"
 #include "testing/platform_test.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 // Test fixture for NotificationPromoWhatsNew.
 class NotificationPromoWhatsNewTest : public PlatformTest {
  public:
   NotificationPromoWhatsNewTest()
       : promo_(&local_state_),
         action_callback_(
             base::Bind(&NotificationPromoWhatsNewTest::OnUserAction,
                        base::Unretained(this))),
@@ skipping 190 matching lines @@
   EXPECT_EQ(1, GetUserActionCount("WhatsNewPromoViewed_RateThisAppPromo"));
 
   // Verify that the promo closed user action count is 0 before |HandleClosed()|
   // is called.
   EXPECT_EQ(0, GetUserActionCount("WhatsNewPromoClosed_RateThisAppPromo"));
   promo_.HandleClosed();
   EXPECT_EQ(1, GetUserActionCount("WhatsNewPromoClosed_RateThisAppPromo"));
 }
 
 }  // namespace