Demo patch that demonstrates simple block layout using Layout NG

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

Index: third_party/WebKit/Source/core/layout/ng/ng_box.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_box.h b/third_party/WebKit/Source/core/layout/ng/ng_box.h
index e2a9e2c3468d32099c831a868dc95aff8a5c3d7a..4efeb6beb1212942c00eef97dbe0676ed50bdccf 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_box.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_box.h
@@ -5,6 +5,7 @@
 #ifndef NGBox_h
 #define NGBox_h
 
+#include "core/layout/ng/ng_box_iterator.h"
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 
@@ -18,20 +19,16 @@ class NGFragment;
 // Represents a node to be laid out.
 class CORE_EXPORT NGBox final {
  public:
-  explicit NGBox(const LayoutObject* layoutObject)
-      : m_layoutObject(layoutObject) {}
+  explicit NGBox(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;
+  LayoutObject* m_layoutObject;
 };
 
 }  // namespace blink