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

ios/chrome/browser/ui/first_run/first_run_util_unittest.mm

Index: ios/chrome/browser/ui/first_run/first_run_util_unittest.mm
diff --git a/ios/chrome/browser/ui/first_run/first_run_util_unittest.mm b/ios/chrome/browser/ui/first_run/first_run_util_unittest.mm
index 3e4270b4ac48d1e7a042b2b5e2126ed983edaca9..5b95b3004b8d6d3842abd3fd28b03b6a506bd142 100644
--- a/ios/chrome/browser/ui/first_run/first_run_util_unittest.mm
+++ b/ios/chrome/browser/ui/first_run/first_run_util_unittest.mm
@@ -4,10 +4,13 @@
 
 #import <UIKit/UIKit.h>
 
-#include "base/mac/scoped_nsobject.h"
 #include "ios/chrome/browser/ui/first_run/first_run_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 TEST(UICommonTest, TestFixOrphanWord) {
@@ -31,8 +34,7 @@ TEST(UICommonTest, TestFixOrphanWord) {
        "那只敏捷的棕色狐狸跃过那只懒狗。快速狐狸";
   // clang-format on
 
-  base::scoped_nsobject<UILabel> label(
-      [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 300, 500)]);
+  UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 300, 500)];
   [label setText:englishString];
   ios_internal::FixOrphanWord(label);
   NSRange range = [[label text] rangeOfString:@"\n"];