[layoutng] Implement state machine for async layout

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

Index: third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc b/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
index 45a8cf6bb7c6536de324d1ad6d399dafeebdbf01..d272fad3714346390d9ade61df62ae9e770d0694 100644
--- a/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
+++ b/third_party/WebKit/Source/core/layout/ng/layout_ng_block_flow.cc
@@ -5,7 +5,6 @@
 #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"
 
@@ -23,9 +22,9 @@ void LayoutNGBlockFlow::layoutBlock(bool relayoutChildren) {
 
   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();
 }