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

ios/chrome/browser/crash_loop_detection_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.
 
 #include "ios/chrome/browser/crash_loop_detection_util.h"
 
 #import <Foundation/Foundation.h>
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 NSString* const kAppStartupFailureCountKey = @"AppStartupFailureCount";
 }
 
 namespace crash_util {
 
 int GetFailedStartupAttemptCount() {
   static int startup_attempt_count = -1;
   if (startup_attempt_count == -1) {
     NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
@@ skipping 13 matching lines @@
 
 void ResetFailedStartupAttemptCount() {
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   if ([defaults integerForKey:kAppStartupFailureCountKey] != 0) {
     [defaults setInteger:0 forKey:kAppStartupFailureCountKey];
     [defaults synchronize];
   }
 }
 
 }  // namespace crash_util