Refactor AppendToFile and WriteFileDescriptor

chrome/browser/media_galleries/linux/mtp_read_file_worker.cc

 // Copyright (c) 2012 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 "chrome/browser/media_galleries/linux/mtp_read_file_worker.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/numerics/safe_conversions.h"
 #include "chrome/browser/media_galleries/linux/snapshot_file_details.h"
 #include "components/storage_monitor/storage_monitor.h"
 #include "content/public/browser/browser_thread.h"
 #include "device/media_transfer_protocol/media_transfer_protocol_manager.h"
 #include "third_party/cros_system_api/dbus/service_constants.h"
 
 using content::BrowserThread;
 using storage_monitor::StorageMonitor;
 
 namespace {
 
 // Appends |data| to the snapshot file specified by the |snapshot_file_path| on
 // the file thread.
 // Returns the number of bytes written to the snapshot file. In case of failure,
 // returns zero.
 uint32 WriteDataChunkIntoSnapshotFileOnFileThread(
     const base::FilePath& snapshot_file_path,
     const std::string& data) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::FILE);
-  int bytes_written =
-      base::AppendToFile(snapshot_file_path, data.data(),
-                         base::checked_cast<int>(data.size()));
-  return (static_cast<int>(data.size()) == bytes_written) ?
-      base::checked_cast<uint32>(bytes_written) : 0;
+  return base::AppendToFile(snapshot_file_path, data.c_str(), data.size())
+             ? base::checked_cast<uint32>(data.size())
+             : 0;
 }
 
 }  // namespace
 
 MTPReadFileWorker::MTPReadFileWorker(const std::string& device_handle)
     : device_handle_(device_handle),
       weak_ptr_factory_(this) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   DCHECK(!device_handle_.empty());
 }
@@ skipping 87 matching lines @@
                    base::File::FILE_ERROR_FAILED));
     return;
   }
   content::BrowserThread::PostTask(
       content::BrowserThread::IO,
       FROM_HERE,
       base::Bind(snapshot_file_details->success_callback(),
                  snapshot_file_details->file_info(),
                  snapshot_file_details->snapshot_file_path()));
 }