[LayoutNG] Switch NGConstraintSpace to being RefCounted.

third_party/WebKit/Source/core/layout/ng/ng_floating_object.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 NGFloatingObject_h
 #define NGFloatingObject_h
 
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_units.h"
@@ skipping 20 matching lines @@
         node(node),
         margins(margins) {
     exclusion_type = NGExclusion::kFloatLeft;
     if (style.floating() == EFloat::kRight)
       exclusion_type = NGExclusion::kFloatRight;
     clear_type = style.clear();
   }
 
   RefPtr<NGPhysicalFragment> fragment;
   // TODO(glebl): Constraint space should be const here.
-  Member<NGConstraintSpace> space;
+  RefPtr<NGConstraintSpace> space;
 
   // Parent space is used so we can calculate the inline offset relative to
   // the original parent of this float.
-  Member<const NGConstraintSpace> original_parent_space;
+  RefPtr<const NGConstraintSpace> original_parent_space;
   Member<NGBlockNode> node;
   NGExclusion::Type exclusion_type;
   EClear clear_type;
   NGBoxStrut margins;
 
   // In the case where a legacy FloatingObject is attached to not its own
   // parent, e.g. a float surrounded by a bunch of nested empty divs,
   // NG float fragment's LeftOffset() cannot be used as legacy FloatingObject's
   // left offset because that offset should be relative to the original float
   // parent.
   // {@code left_offset} is calculated when we know to which parent this float
   // would be attached.
   LayoutUnit left_offset;
 
   DEFINE_INLINE_TRACE() {
-    visitor->trace(space);
-    visitor->trace(original_parent_space);
     visitor->trace(node);
   }
 };
 
 }  // namespace blink
 
 #endif  // NGFloatingObject_h