Switch to new SmbFileSystem readdir method

-Switches SmbFileSystem to using the new Start/Continue ReadDirectory flow

Bug: chromium:757625
Change-Id: I7e6501b90c4158775440871125dba0d05df7b508
Reviewed-on: https://chromium-review.googlesource.com/1231918
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595288}

chrome/browser/chromeos/smb_client/smb_file_system.cc

@@ -230,16 +230,11 @@ AbortCallback SmbFileSystem::ExecuteAction(
 AbortCallback SmbFileSystem::ReadDirectory(
     const base::FilePath& directory_path,
     storage::AsyncFileUtil::ReadDirectoryCallback callback) {
-  base::ElapsedTimer metrics_timer;
+  OperationId operation_id = task_queue_.GetNextOperationId();
 
-  auto reply =
-      base::BindOnce(&SmbFileSystem::HandleRequestReadDirectoryCallback,
-                     AsWeakPtr(), callback, std::move(metrics_timer));
-  SmbTask task = base::BindOnce(&SmbProviderClient::ReadDirectory,
-                                GetWeakSmbProviderClient(), GetMountId(),
-                                directory_path, std::move(reply));
+  StartReadDirectory(directory_path, operation_id, std::move(callback));
 
-  return EnqueueTaskAndGetCallback(std::move(task));
+  return CreateAbortCallback(operation_id);
 }
 
 AbortCallback SmbFileSystem::OpenFile(const base::FilePath& file_path,