[LayoutNG] Switch NGConstraintSpace to being RefCounted.

third_party/WebKit/Source/core/layout/ng/ng_out_of_flow_layout_part.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/ng_out_of_flow_layout_part.h"
 
 #include "core/layout/ng/ng_absolute_utils.h"
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_box_fragment.h"
 #include "core/layout/ng/ng_constraint_space_builder.h"
@@ skipping 160 matching lines @@
 
   NGLogicalSize available_size{inline_size, block_size};
 
   NGConstraintSpaceBuilder builder(container_space_->WritingMode());
   builder.SetAvailableSize(available_size);
   builder.SetPercentageResolutionSize(container_space_->AvailableSize());
   if (block_estimate)
     builder.SetIsFixedSizeBlock(true);
   builder.SetIsFixedSizeInline(true);
   builder.SetIsNewFormattingContext(true);
-  NGConstraintSpace* space =
+  RefPtr<NGConstraintSpace> space =
       builder.ToConstraintSpace(container_space_->WritingMode());
 
-  return descendant.Layout(space);
+  return descendant.Layout(space.get());
 }
 
 }  // namespace blink