[LayoutNG] Remove derived constraint spaces from opportunity iterator.

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/text/WTFString.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
-typedef const NGConstraintSpace NGLayoutOpportunity;
-typedef HeapVector<Member<const NGLayoutOpportunity>> NGLayoutOpportunities;
+typedef NGLogicalRect NGLayoutOpportunity;
+typedef Vector<NGLayoutOpportunity> NGLayoutOpportunities;
 
 class CORE_EXPORT NGLayoutOpportunityIterator final
-    : public GarbageCollected<NGLayoutOpportunityIterator> {
+    : public GarbageCollectedFinalized<NGLayoutOpportunityIterator> {
  public:
   NGLayoutOpportunityIterator(NGConstraintSpace* space,
                               unsigned clear,
                               bool for_inline_or_bfc);
 
   // Gets the next Layout Opportunity or nullptr if the search is exhausted.
   // TODO(chrome-layout-team): Refactor with using C++ <iterator> library.
-  NGLayoutOpportunity* Next();
+  const NGLayoutOpportunity Next();
 
   DEFINE_INLINE_VIRTUAL_TRACE() {
     visitor->trace(constraint_space_);
-    visitor->trace(opportunities_);
     visitor->trace(opportunity_tree_root_);
   }
 
  private:
   Member<NGConstraintSpace> constraint_space_;
 
   NGLayoutOpportunities opportunities_;
-  Vector<Member<NGLayoutOpportunity>>::const_iterator opportunity_iter_;
+  NGLayoutOpportunities::const_iterator opportunity_iter_;
   Member<NGLayoutOpportunityTreeNode> opportunity_tree_root_;
 };
 
 }  // namespace blink
 
 #endif  // NGLayoutOpportunityIterator_h