Curring a lambda

native_file_system_file_handle.cc

// -- snip --  
manager()->CreateSwapFileForURL(
      url(),
      base::BindOnce([](CreateFileWriterCallback callback) {
                        base::File::Error result,
                        const storage::FileSystemURL& swap_url) {
                       // Canned answer for now.
                       std::move(callback).Run(
                           NativeFileSystemError::New(base::File::FILE_OK),
                           nullptr);
                     }, std::move(callback)));
// -- snip --

native_file_system_manager_impl.h

//  -- snip --
  template <typename CallbackArgType>
      void NativeFileSystemManagerImpl::CreateSwapFileForURL(
          const storage::FileSystemURL& url,
          base::OnceCallback<void(CallbackArgType)> callback) {
    base::FilePath swap_path = base::GetUniquePath(
        base::FilePath(url.path()).AddExtensionASCII(".crswap"));
    auto url_and_handle = CreateFileSystemURLFromPath(url.origin(), swap_path);
    auto swap_url = url_and_handle.url;
    operation_runner()->CreateFile(
        swap_url,
        /*exclusive*/true,
        base::BindOnce(&NativeFileSystemManagerImpl::DidCreateSwapFile,
                       weak_factory_.GetWeakPtr(),
                       std::move(swap_url),
                       std::move(callback)));
  }

  template <typename CallbackArgType>
      void NativeFileSystemManagerImpl::DidCreateSwapFile(
          const storage::FileSystemURL& swap_url,
          base::OnceCallback<void(CallbackArgType)> callback,
          base::File::Error result) {
    std::move(callback).Run(std::move(result), std::move(swap_url));
  }
  // -- snip --