Revert of [LayoutNG] Initial implementation of NGBoxIterator

third_party/WebKit/Source/core/layout/ng/ng_box_iterator.h

-// Copyright 2016 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 NGBoxIterator_h
-#define NGBoxIterator_h
-
-#include "core/layout/LayoutObject.h"
-
-namespace blink {
-
-class NGBox;
-
-// NG Box iterator over siblings of the layout object.
-class NGBoxIterator {
- public:
-  explicit NGBoxIterator(const LayoutObject*);
-  NGBox first();
-  NGBox next();
-
- private:
-  void reset();
-
-  const LayoutObject* m_layoutObject;
-  const LayoutObject* m_currentChild;
-};
-
-}  // namespace blink
-#endif  // NGBoxIterator_h