Revert of Move some sync/notifier to components/invalidation

sync/notifier/state_writer.h

+// Copyright 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_
+
+#include <string>
+
+#include "sync/base/sync_export.h"
+
+namespace syncer {
+
+class SYNC_EXPORT_PRIVATE StateWriter {
+ public:
+  virtual ~StateWriter() {}
+
+  virtual void WriteState(const std::string& state) = 0;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_NOTIFIER_STATE_WRITER_H_