(For-try) Divide recursive Copy/Move into multiple async tasks

chrome/browser/media_gallery/win/mtp_device_delegate_impl_win.cc

 // Copyright (c) 2013 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.
 //
 // MTPDeviceDelegateImplWin implementation.
 
 #include "chrome/browser/media_gallery/win/mtp_device_delegate_impl_win.h"
 
 #include <portabledevice.h>
 
@@ skipping 149 matching lines @@
     const FilePath& local_path,
     base::PlatformFileInfo* file_info) {
   if (!LazyInit())
     return base::PLATFORM_FILE_ERROR_FAILED;
   string16 file_object_id = GetFileObjectIdFromPath(device_file_path.value());
   if (file_object_id.empty())
     return base::PLATFORM_FILE_ERROR_FAILED;
   base::PlatformFileError error = GetFileInfo(device_file_path, file_info);
   if (error != base::PLATFORM_FILE_OK)
     return error;
+  if (file_info->is_directory)
+    return base::PLATFORM_FILE_ERROR_NOT_A_FILE;
   if (!media_transfer_protocol::WriteFileObjectContentToPath(device_.get(),
                                                              file_object_id,
                                                              local_path))
     return base::PLATFORM_FILE_ERROR_FAILED;
 
   // LocalFileStreamReader is used to read the contents of the snapshot file.
   // Snapshot file modification time does not match the last modified time
   // of the original media file. Therefore, set the last modified time to null
   // in order to avoid the verification in LocalFileStreamReader.
   //
@@ skipping 50 matching lines @@
     file_object_id = media_transfer_protocol::GetObjectIdFromName(device_,
                                                                   parent_id,
                                                                   *path_iter);
     if (file_object_id.empty())
       break;
     parent_id = file_object_id;
   }
   return file_object_id;
 }
 
-}  // namespace chrome
+}  // namespace chrome