[ObjC ARC] Converts ios/chrome/common/app_group:main_app to ARC.

ios/chrome/common/app_group/app_group_metrics_mainapp.h

 // 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.
 
 #ifndef IOS_CHROME_COMMON_APP_GROUP_APP_GROUP_METRICS_MAINAPP_H_
 #define IOS_CHROME_COMMON_APP_GROUP_APP_GROUP_METRICS_MAINAPP_H_
 
 #import <Foundation/Foundation.h>
 #include <stdint.h>
 
-#include "base/mac/scoped_block.h"
 #include "ios/chrome/common/app_group/app_group_constants.h"
 
 namespace app_group {
 
 typedef void (^ProceduralBlockWithData)(NSData*);
 
 // These methods must be called from the Chrome app.
 namespace main_app {
 
 // Iterates through the extensions pending logs and deletes them.
 // Calls |callback| on each log before deleting.
-void ProcessPendingLogs(
-    const base::mac::ScopedBlock<ProceduralBlockWithData>& callback);
+void ProcessPendingLogs(ProceduralBlockWithData callback);
 
 // Enables the metrics collecting in extensions. The extensions will
 // use |clientID| as client ID, and |brandCode| as brand code in the logs.
 void EnableMetrics(NSString* client_id,
                    NSString* brand_code,
                    int64_t installDate,
                    int64_t enableMetricsDate);
 
 // Disabled the metrics collecting in extensions.
 void DisableMetrics();
 
 }  // namespace main_app
 }  // namespace app_group
 
 #endif  // IOS_CHROME_COMMON_APP_GROUP_APP_GROUP_METRICS_MAINAPP_H_