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

ios/chrome/browser/ui/settings/do_not_track_collection_view_controller_unittest.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.
 
 #import "ios/chrome/browser/ui/settings/do_not_track_collection_view_controller.h"
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
-#import "base/mac/scoped_nsobject.h"
 #include "base/message_loop/message_loop.h"
 #include "components/prefs/pref_member.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/sync_preferences/pref_service_mock_factory.h"
 #include "ios/chrome/browser/pref_names.h"
 #import "ios/chrome/browser/ui/collection_view/collection_view_controller_test.h"
 #include "ios/chrome/grit/ios_strings.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #import "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 class DoNotTrackCollectionViewControllerTest
     : public CollectionViewControllerTest {
  protected:
   void SetUp() override {
     CollectionViewControllerTest::SetUp();
     pref_service_ = CreateLocalState();
   }
 
-  CollectionViewController* NewController() override NS_RETURNS_RETAINED {
+  CollectionViewController* InstantiateController() override {
     return [[DoNotTrackCollectionViewController alloc]
         initWithPrefs:pref_service_.get()];
   }
 
   std::unique_ptr<PrefService> CreateLocalState() {
     scoped_refptr<PrefRegistrySimple> registry(new PrefRegistrySimple());
     registry->RegisterBooleanPref(prefs::kEnableDoNotTrack, false);
     base::FilePath path("DoNotTrackCollectionViewControllerTest.pref");
 
     sync_preferences::PrefServiceMockFactory factory;
@@ skipping 19 matching lines @@
   doNotTrackEnabled.Init(prefs::kEnableDoNotTrack, pref_service_.get());
   doNotTrackEnabled.SetValue(true);
   CreateController();
   EXPECT_EQ(2, NumberOfSections());
   EXPECT_EQ(1, NumberOfItemsInSection(0));
   CheckSwitchCellStateAndTitleWithId(YES, IDS_IOS_OPTIONS_DO_NOT_TRACK_MOBILE,
                                      0, 0);
 }
 
 }  // namespace