[ObjC ARC] Converts ios/chrome/browser/crash_report to ARC

ios/chrome/browser/crash_report/crash_report_background_uploader.mm

 // Copyright 2014 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/crash_report/crash_report_background_uploader.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_block.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
 #include "base/time/time.h"
 #import "breakpad/src/client/ios/BreakpadController.h"
 #include "ios/chrome/browser/experimental_flags.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using base::UserMetricsAction;
 
 namespace {
 
 NSString* const kBackgroundReportUploader =
     @"com.google.chrome.breakpad.backgroundupload";
 const char* const kUMAMobileCrashBackgroundUploadDelay =
     "CrashReport.CrashBackgroundUploadDelay";
 const char* const kUMAMobilePendingReportsOnBackgroundWakeUp =
     "CrashReport.PendingReportsOnBackgroundWakeUp";
@@ skipping 29 matching lines @@
   BOOL _didFinishEventsCalled;
 }
 
 + (instancetype)sharedInstance {
   static UrlSessionDelegate* instance = [[UrlSessionDelegate alloc] init];
   return instance;
 }
 
 - (void)setSessionCompletionHandler:(ProceduralBlock)completionHandler {
   DCHECK(completionHandler);
-  _sessionCompletionHandler.reset(completionHandler,
-                                  base::scoped_policy::RETAIN);
+  _sessionCompletionHandler.reset(completionHandler);
   _didFinishEventsCalled = NO;
 }
 
 - (void)URLSession:(NSURLSession*)session
                    task:(NSURLSessionTask*)dataTask
     didReceiveChallenge:(NSURLAuthenticationChallenge*)challenge
       completionHandler:
           (void (^)(NSURLSessionAuthChallengeDisposition disposition,
                     NSURLCredential* credential))completionHandler {
   if (![challenge.protectionSpace.authenticationMethod
@@ skipping 273 matching lines @@
           integerForKey:kReportsUploadedInBackground];
   return uploadedCrashReportsInBackgroundCount > 0;
 }
 
 + (void)resetReportsUploadedInBackgroundCount {
   [[NSUserDefaults standardUserDefaults]
       removeObjectForKey:kReportsUploadedInBackground];
 }
 
 @end