[ObjC ARC] Converts ios/chrome/app:app_internal to ARC.

ios/chrome/app/startup_tasks.mm

 // Copyright 2016 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/app/startup_tasks.h"
 
 #import <MediaPlayer/MediaPlayer.h>
 
-#import "base/ios/weak_nsobject.h"
 #import "base/mac/bind_objc_block.h"
 #include "components/bookmarks/browser/startup_task_runner_service.h"
 #import "ios/chrome/app/deferred_initialization_runner.h"
 #include "ios/chrome/app/tests_hook.h"
 #include "ios/chrome/browser/application_context.h"
 #include "ios/chrome/browser/bookmarks/startup_task_runner_service_factory.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/ios_chrome_io_thread.h"
 #import "ios/chrome/browser/omaha/omaha_service.h"
 #include "ios/chrome/browser/reading_list/reading_list_download_service.h"
 #include "ios/chrome/browser/reading_list/reading_list_download_service_factory.h"
 #import "ios/chrome/browser/ui/main/browser_view_information.h"
 #import "ios/chrome/browser/upgrade/upgrade_center.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // Constants for deferred initilization of the profile start-up task runners.
 NSString* const kStartProfileStartupTaskRunners =
     @"StartProfileStartupTaskRunners";
 }  // namespace
 
 @interface StartupTasks ()
 
 // Performs browser state initialization tasks that don't need to happen
 // synchronously at startup.
@@ skipping 61 matching lines @@
   NSDictionary* nowPlayingInfo =
       [[MPNowPlayingInfoCenter defaultCenter] nowPlayingInfo];
   if (nowPlayingInfo[MPMediaItemPropertyTitle]) {
     // No need to clear playing info if media is being played but there is no
     // way to check if video or audio is playing in web view.
     [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:nil];
   }
 }
 
 @end