[ObjC ARC] Converts ios/web/app to ARC

ios/web/app/web_main_loop.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.
 
 #include "ios/web/app/web_main_loop.h"
 
 #include <stddef.h>
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/path_service.h"
 #include "base/power_monitor/power_monitor.h"
 #include "base/power_monitor/power_monitor_device_source.h"
 #include "base/process/process_metrics.h"
 #include "base/system_monitor/system_monitor.h"
 #include "base/threading/thread_restrictions.h"
 #include "ios/web/net/cookie_notification_bridge.h"
 #include "ios/web/public/app/web_main_parts.h"
 #include "ios/web/public/web_client.h"
 #include "ios/web/web_thread_impl.h"
 #include "ios/web/webui/url_data_manager_ios.h"
 #include "net/base/network_change_notifier.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 // The currently-running WebMainLoop.  There can be one or zero.
 // TODO(rohitrao): Desktop uses this to implement
 // ImmediateShutdownAndExitProcess.  If we don't need that functionality, we can
 // remove this.
 WebMainLoop* g_current_web_main_loop = nullptr;
 
 WebMainLoop::WebMainLoop() : result_code_(0), created_threads_(false) {
   DCHECK(!g_current_web_main_loop);
@@ skipping 221 matching lines @@
   main_thread_.reset(
       new WebThreadImpl(WebThread::UI, base::MessageLoop::current()));
 }
 
 int WebMainLoop::WebThreadsStarted() {
   cookie_notification_bridge_.reset(new CookieNotificationBridge);
   return result_code_;
 }
 
 }  // namespace web