[LayoutNG] Stack allocate NGLayoutOpportunityIterator.

third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.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 NGLayoutOpportunityIterator_h
 #define NGLayoutOpportunityIterator_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_layout_opportunity_tree_node.h"
 #include "core/layout/ng/ng_units.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Optional.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 typedef NGLogicalRect NGLayoutOpportunity;
 typedef Vector<NGLayoutOpportunity> NGLayoutOpportunities;
 
-class CORE_EXPORT NGLayoutOpportunityIterator final
-    : public GarbageCollectedFinalized<NGLayoutOpportunityIterator> {
+class CORE_EXPORT NGLayoutOpportunityIterator final {
+  STACK_ALLOCATED();
+
  public:
   // Default constructor.
   //
   // @param space Constraint space with exclusions for which this iterator needs
   //              to generate layout opportunities.
   // @param opt_origin_point Optional origin_point parameter that is used as a
   //                         default start point for layout opportunities.
   // @param opt_leader_point Optional 'leader' parameter that is used to specify
   //                         the ending point of temporary excluded rectangle
   //                         which starts from 'origin'. This rectangle may
   //                         represent a text fragment for example.
   NGLayoutOpportunityIterator(
       NGConstraintSpace* space,
       const WTF::Optional<NGLogicalOffset>& opt_origin_point = WTF::nullopt,
       const WTF::Optional<NGLogicalOffset>& opt_leader_point = WTF::nullopt);
 
   // Gets the next Layout Opportunity or nullptr if the search is exhausted.
   // TODO(chrome-layout-team): Refactor with using C++ <iterator> library.
   const NGLayoutOpportunity Next();
 
-  DEFINE_INLINE_VIRTUAL_TRACE() {
-    visitor->trace(constraint_space_);
-    visitor->trace(opportunity_tree_root_);
-  }
-
  private:
   // Mutable Getters.
   NGLayoutOpportunityTreeNode* MutableOpportunityTreeRoot() {
     return opportunity_tree_root_.get();
   }
 
   // Read-only Getters.
   const NGLayoutOpportunityTreeNode* OpportunityTreeRoot() const {
     return opportunity_tree_root_.get();
   }
 
-  Member<NGConstraintSpace> constraint_space_;
+  Persistent<NGConstraintSpace> constraint_space_;
 
   NGLayoutOpportunities opportunities_;
   NGLayoutOpportunities::const_iterator opportunity_iter_;
-  Member<NGLayoutOpportunityTreeNode> opportunity_tree_root_;
+  Persistent<NGLayoutOpportunityTreeNode> opportunity_tree_root_;
 };
 
 }  // namespace blink
 
 #endif  // NGLayoutOpportunityIterator_h