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

ios/chrome/browser/ui/show_privacy_settings_util.mm

 // Copyright 2013 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/show_privacy_settings_util.h"
 
-#import "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h"
 #import "ios/chrome/browser/ui/commands/generic_chrome_command.h"
 #include "ios/chrome/browser/ui/commands/ios_command_ids.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 void ShowClearBrowsingData() {
-  base::scoped_nsobject<GenericChromeCommand> command(
-      [[GenericChromeCommand alloc]
-          initWithTag:IDC_SHOW_CLEAR_BROWSING_DATA_SETTINGS]);
+  GenericChromeCommand* command = [[GenericChromeCommand alloc]
+      initWithTag:IDC_SHOW_CLEAR_BROWSING_DATA_SETTINGS];
   UIWindow* main_window = [[UIApplication sharedApplication] keyWindow];
   [main_window chromeExecuteCommand:command];
 }