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

chrome/browser/media_gallery/linux/mtp_device_delegate_impl_linux.cc

Index: chrome/browser/media_gallery/linux/mtp_device_delegate_impl_linux.cc
diff --git a/chrome/browser/media_gallery/linux/mtp_device_delegate_impl_linux.cc b/chrome/browser/media_gallery/linux/mtp_device_delegate_impl_linux.cc
index 6a5e2c1816a21f88c153a29d4e0845b64590e474..cd1f87792074c92cdc09c64298d5ddedb3cd8ee6 100644
--- a/chrome/browser/media_gallery/linux/mtp_device_delegate_impl_linux.cc
+++ b/chrome/browser/media_gallery/linux/mtp_device_delegate_impl_linux.cc
@@ -133,6 +133,8 @@ PlatformFileError MTPDeviceDelegateImplLinux::CreateSnapshotFile(
   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 (file_info->size <= 0 || file_info->size > kuint32max)
     return base::PLATFORM_FILE_ERROR_FAILED;