Original patch by rlarocque@chromium.org at http://codereview.chromium.org/7633077/

chrome/browser/sync/internal_api/write_transaction.h

Index: chrome/browser/sync/internal_api/write_transaction.h
diff --git a/chrome/browser/sync/internal_api/write_transaction.h b/chrome/browser/sync/internal_api/write_transaction.h
new file mode 100644
index 0000000000000000000000000000000000000000..e90abc7f467b20334c39442c0b11ae9b32ac4612
--- /dev/null
+++ b/chrome/browser/sync/internal_api/write_transaction.h
@@ -0,0 +1,56 @@
+// 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_INTERNAL_API_WRITE_TRANSACTION_H_
+#define CHROME_BROWSER_SYNC_INTERNAL_API_WRITE_TRANSACTION_H_
+
+#include "base/basictypes.h"
+#include "chrome/browser/sync/internal_api/base_transaction.h"
+
+namespace syncable {
+class BaseTransaction;
+class WriteTransaction;
+}  // namespace syncable
+
+namespace tracked_objects {
+class Location;
+}  // namespace tracked_objects
+
+namespace sync_api {
+
+// Sync API's WriteTransaction is a read/write BaseTransaction.  It wraps
+// a syncable::WriteTransaction.
+//
+// NOTE: Only a single model type can be mutated for a given
+// WriteTransaction.
+class WriteTransaction : public BaseTransaction {
+ public:
+  // Start a new read/write transaction.
+  WriteTransaction(const tracked_objects::Location& from_here,
+                   UserShare* share);
+  virtual ~WriteTransaction();
+
+  // Provide access to the syncable.h transaction from the API WriteNode.
+  virtual syncable::BaseTransaction* GetWrappedTrans() const;
+  syncable::WriteTransaction* GetWrappedWriteTrans() { return transaction_; }
+
+ protected:
+  WriteTransaction() {}
+
+  void SetTransaction(syncable::WriteTransaction* trans) {
+      transaction_ = trans;
+  }
+
+ private:
+  void* operator new(size_t size);  // Transaction is meant for stack use only.
+
+  // The underlying syncable object which this class wraps.
+  syncable::WriteTransaction* transaction_;
+
+  DISALLOW_COPY_AND_ASSIGN(WriteTransaction);
+};
+
+} // namespace sync_api
+
+#endif  // CHROME_BROWSER_SYNC_INTERNAL_API_WRITE_TRANSACTION_H_