[LayoutNG] Initial implementation of NGBoxIterator

third_party/WebKit/Source/core/layout/ng/ng_box.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 NGBox_h
 #define NGBox_h
 
+#include "core/layout/ng/ng_box_iterator.h"
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class ComputedStyle;
 class LayoutObject;
 class NGConstraintSpace;
 class NGFragment;
 
 // Represents a node to be laid out.
 class CORE_EXPORT NGBox final {
  public:
   explicit NGBox(const LayoutObject* layoutObject)
       : m_layoutObject(layoutObject) {}
 
+  NGBoxIterator iterator() { return NGBoxIterator(m_layoutObject); }
   operator bool() const { return m_layoutObject; }
 
   NGFragment* layout(const NGConstraintSpace&);
   const ComputedStyle* style() const;
 
-  // TODO(layout-ng): Returning a children iterator would be better here.
-  const NGBox firstChild() const;
-  const NGBox nextSibling() const;
-
  private:
   const LayoutObject* m_layoutObject;
 };
 
 }  // namespace blink
 
 #endif  // NGBox_h