[Sync] Rename csync namespace to syncer

sync/notifier/state_writer.h

 // Copyright (c) 2012 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.
 //
 // Simple interface for something that persists state.
 
 #ifndef SYNC_NOTIFIER_STATE_WRITER_H_
 #define SYNC_NOTIFIER_STATE_WRITER_H_
 #pragma once
 
 #include <string>
 
-namespace csync {
+namespace syncer {
 
 class StateWriter {
  public:
   virtual ~StateWriter() {}
 
   virtual void WriteState(const std::string& state) = 0;
 };
 
-}  // sync_notifier
+}  // namespace syncer
 
 #endif  // SYNC_NOTIFIER_STATE_WRITER_H_