iwyu: Use callback_old.h where appropriate, part 2.

chrome/browser/sync/engine/syncapi.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.
 
 // This file defines the "sync API", an interface to the syncer
 // backend that exposes (1) the core functionality of maintaining a consistent
 // local snapshot of a hierarchical object set; (2) a means to transactionally
 // access and modify those objects; (3) a means to control client/server
 // synchronization tasks, namely: pushing local object modifications to a
 // server, pulling nonlocal object modifications from a server to this client,
@@ skipping 25 matching lines @@
 // children of a node can be enumerated in the order of their position.
 
 #ifndef CHROME_BROWSER_SYNC_ENGINE_SYNCAPI_H_
 #define CHROME_BROWSER_SYNC_ENGINE_SYNCAPI_H_
 #pragma once
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
-#include "base/callback.h"
+#include "base/callback_old.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/tracked.h"
 #include "build/build_config.h"
 #include "chrome/browser/sync/engine/configure_reason.h"
 #include "chrome/browser/sync/protocol/password_specifics.pb.h"
 #include "chrome/browser/sync/syncable/autofill_migration.h"
 #include "chrome/browser/sync/syncable/model_type.h"
 #include "chrome/browser/sync/util/cryptographer.h"
 #include "chrome/common/net/gaia/google_service_auth_error.h"
@@ skipping 974 matching lines @@
  private:
   // An opaque pointer to the nested private class.
   SyncInternal* data_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncManager);
 };
 
 }  // namespace sync_api
 
 #endif  // CHROME_BROWSER_SYNC_ENGINE_SYNCAPI_H_