Add ShowLayoutOpportunityTree to 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_layout_opportunity_tree_node.h"
 #include "platform/heap/Handle.h"
@@ skipping 20 matching lines @@
   //                         represent a text fragment for example.
   NGLayoutOpportunityIterator(
       const 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();
 
+#ifndef NDEBUG
+  // Prints Layout Opportunity tree for debug purposes.
+  void ShowLayoutOpportunityTree() const;
+#endif
+
  private:
   // Mutable Getters.
   NGLayoutOpportunityTreeNode* MutableOpportunityTreeRoot() {
     return opportunity_tree_root_.get();
   }
 
   // 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_;
 };
 
 }  // namespace blink
 
 #endif  // NGLayoutOpportunityIterator_h