Converts ios/web/net to ARC.

ios/web/net/request_tracker_factory_impl.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/net/request_tracker_factory_impl.h"
 
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/sys_string_conversions.h"
 #include "ios/web/net/request_group_util.h"
 #include "ios/web/net/request_tracker_impl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace web {
 
 RequestTrackerFactoryImpl::RequestTrackerFactoryImpl(
     const std::string& application_scheme) {
   if (!application_scheme.empty()) {
     application_scheme_.reset(
         [base::SysUTF8ToNSString(application_scheme) copy]);
     DCHECK(application_scheme_);
   }
 }
@@ skipping 17 matching lines @@
       RequestTrackerImpl::GetTrackerForRequestGroupID(request_group_id);
   if (tracker_impl)
     *tracker = tracker_impl->GetWeakPtr();
   // If there is a request group ID, but no associated tracker, return false.
   // This usually happens when the tab has been closed, but can maybe also
   // happen in other cases (see http://crbug.com/228397).
   return tracker->get() != nullptr;
 }
 
 }  // namespace web