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

chrome/browser/sync/internal_api/base_transaction.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_INTERNAL_API_BASE_TRANSACTION_H_
+#define CHROME_BROWSER_SYNC_INTERNAL_API_BASE_TRANSACTION_H_
+#pragma once
+
+#include "chrome/browser/sync/internal_api/user_share.h"
+
+#include "chrome/browser/sync/util/cryptographer.h"
+
+namespace syncable {
+class BaseTransaction;
+class ScopedDirLookup;
+}
+
+namespace sync_api {
+
+// Sync API's BaseTransaction, ReadTransaction, and WriteTransaction allow for
+// batching of several read and/or write operations.  The read and write
+// operations are performed by creating ReadNode and WriteNode instances using
+// the transaction. These transaction classes wrap identically named classes in
+// syncable, and are used in a similar way. Unlike syncable::BaseTransaction,
+// whose construction requires an explicit syncable::ScopedDirLookup, a sync
+// API BaseTransaction creates its own ScopedDirLookup implicitly.
+class BaseTransaction {
+ public:
+  // Provide access to the underlying syncable.h objects from BaseNode.
+  virtual syncable::BaseTransaction* GetWrappedTrans() const = 0;
+  const syncable::ScopedDirLookup& GetLookup() const { return *lookup_; }
+  browser_sync::Cryptographer* GetCryptographer() const {
+    return cryptographer_;
+  }
+
+ protected:
+  // The ScopedDirLookup is created in the constructor and destroyed
+  // in the destructor.  Creation of the ScopedDirLookup is not expected
+  // to fail.
+  explicit BaseTransaction(UserShare* share);
+  virtual ~BaseTransaction();
+
+  BaseTransaction() { lookup_= NULL; }
+
+ private:
+  // A syncable ScopedDirLookup, which is the parent of syncable transactions.
+  syncable::ScopedDirLookup* lookup_;
+
+  browser_sync::Cryptographer* cryptographer_;
+
+  DISALLOW_COPY_AND_ASSIGN(BaseTransaction);
+};
+
+syncable::ModelTypeSet GetEncryptedTypes(
+    const sync_api::BaseTransaction* trans);
+
+}  // namespace sync_api
+
+#endif  // CHROME_BROWSER_SYNC_INTERNAL_API_BASE_TRANSACTION_H_