Move NGLayoutOpportunityTreeNode off Oilpan

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_layout_opportunity_tree_node.h"
-#include "platform/heap/Handle.h"
 #include "wtf/Optional.h"
 #include "wtf/Vector.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace blink {
 
 class NGConstraintSpace;
 typedef NGLogicalRect NGLayoutOpportunity;
 typedef Vector<NGLayoutOpportunity> NGLayoutOpportunities;
 
@@ skipping 35 matching lines @@
 
   // Read-only Getters.
   const NGLayoutOpportunityTreeNode* OpportunityTreeRoot() const {
     return opportunity_tree_root_.get();
   }
 
   const NGConstraintSpace* constraint_space_;
 
   NGLayoutOpportunities opportunities_;
   NGLayoutOpportunities::const_iterator opportunity_iter_;
-  Persistent<NGLayoutOpportunityTreeNode> opportunity_tree_root_;
+  std::unique_ptr<NGLayoutOpportunityTreeNode> opportunity_tree_root_;
   NGLogicalOffset offset_;
 };
 
 }  // namespace blink
 
 #endif  // NGLayoutOpportunityIterator_h