[layoutng] Implement state machine for async layout

third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc

 // 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.
 
 #include "core/layout/ng/layout_ng_block_flow.h"
 #include "core/layout/ng/ng_derived_constraint_space.h"
 #include "core/layout/ng/ng_block_layout_algorithm.h"
-#include "core/layout/ng/ng_box_iterator.h"
 #include "core/layout/ng/ng_fragment.h"
 #include "core/layout/LayoutAnalyzer.h"
 
 namespace blink {
 
 LayoutNGBlockFlow::LayoutNGBlockFlow(Element* element)
     : LayoutBlockFlow(element) {}
 
 bool LayoutNGBlockFlow::isOfType(LayoutObjectType type) const {
   return type == LayoutObjectNGBlockFlow || LayoutBlockFlow::isOfType(type);
 }
 
 void LayoutNGBlockFlow::layoutBlock(bool relayoutChildren) {
   LayoutAnalyzer::BlockScope analyzer(*this);
 
   const auto* constraint_space =
       NGDerivedConstraintSpace::CreateFromLayoutObject(*this);
-  NGBox box(this);
+  NGBox* box = new NGBox(this);
   NGFragment* fragment;
-  while (!box.Layout(constraint_space, &fragment))
+  while (!box->Layout(constraint_space, &fragment))
     ;
   clearNeedsLayout();
 }
 
 }  // namespace blink