[Sync] Split DirectoryChangeListener for thread-safety

chrome/test/sync/null_directory_change_delegate.h

+// Copyright (c) 2011 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.
+
+#ifndef CHROME_TEST_SYNC_NULL_DIRECTORY_CHANGE_DELEGATE_H_
+#define CHROME_TEST_SYNC_NULL_DIRECTORY_CHANGE_DELEGATE_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "chrome/browser/sync/syncable/directory_change_delegate.h"
+
+namespace syncable {
+
+// DirectoryChangeDelegate that does nothing in all delegate methods.
+class NullDirectoryChangeDelegate : public DirectoryChangeDelegate {
+ public:
+  virtual ~NullDirectoryChangeDelegate();
+
+  virtual void HandleCalculateChangesChangeEventFromSyncApi(
+      const OriginalEntries& originals,
+      BaseTransaction* trans) OVERRIDE;
+  virtual void HandleCalculateChangesChangeEventFromSyncer(
+      const OriginalEntries& originals,
+      BaseTransaction* trans) OVERRIDE;
+  virtual ModelTypeBitSet HandleTransactionEndingChangeEvent(
+      BaseTransaction* trans) OVERRIDE;
+  virtual void HandleTransactionCompleteChangeEvent(
+      const ModelTypeBitSet& models_with_changes) OVERRIDE;
+};
+
+}  // namespace syncable
+
+#endif  // CHROME_TEST_SYNC_NULL_DIRECTORY_CHANGE_DELEGATE_H_