[Sync] Split DirectoryChangeListener for thread-safety

chrome/browser/sync/syncable/transaction_observer.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_BROWSER_SYNC_SYNCABLE_TRANSACTION_OBSERVER_H_
+#define CHROME_BROWSER_SYNC_SYNCABLE_TRANSACTION_OBSERVER_H_
+#pragma once
+
+#include "chrome/browser/sync/syncable/model_type.h"
+#include "chrome/browser/sync/syncable/syncable.h"
+
+namespace tracked_objects {
+class Location;
+}  // namespace tracked_objects
+
+namespace syncable {
+
+class TransactionObserver {
+ public:
+  virtual void OnTransactionStart(
+      const tracked_objects::Location& location,
+      const WriterTag& writer) = 0;
+  virtual void OnTransactionMutate(
+      const tracked_objects::Location& location,
+      const WriterTag& writer,
+      // TODO(akalin): Have pairs of old/new entries instead of just
+      // the originals.
+      const OriginalEntries& originals,
+      const ModelTypeBitSet& models_with_changes) = 0;
+  virtual void OnTransactionEnd(
+      const tracked_objects::Location& location,
+      const WriterTag& writer) = 0;
+ protected:
+  virtual ~TransactionObserver() {}
+};
+
+}  // namespace syncable
+
+#endif  // CHROME_BROWSER_SYNC_SYNCABLE_TRANSACTION_OBSERVER_H_