Change NGLayoutOpportunityIterator constructor to work with const CS.

third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc

 // 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.
 
 #include "core/layout/ng/ng_layout_opportunity_iterator.h"
 
 #include "core/layout/ng/ng_units.h"
 #include "wtf/NonCopyingSort.h"
 
 namespace blink {
@@ skipping 214 matching lines @@
 
   NGExclusion leader_exclusion;
   leader_exclusion.rect.offset = origin_point;
   leader_exclusion.rect.size = {inline_size, block_size};
   return leader_exclusion;
 }
 
 }  // namespace
 
 NGLayoutOpportunityIterator::NGLayoutOpportunityIterator(
-    NGConstraintSpace* space,
+    const NGConstraintSpace* space,
     const WTF::Optional<NGLogicalOffset>& opt_origin_point,
     const WTF::Optional<NGLogicalOffset>& opt_leader_point)
     : constraint_space_(space) {
   // TODO(chrome-layout-team): Combine exclusions that shadow each other.
   auto& exclusions = constraint_space_->Exclusions();
   DCHECK(std::is_sorted(exclusions->storage.begin(), exclusions->storage.end(),
                         &CompareNGExclusionsByTopAsc))
       << "Exclusions are expected to be sorted by TOP";
 
   NGLogicalOffset origin_point =
@@ skipping 23 matching lines @@
 
 const NGLayoutOpportunity NGLayoutOpportunityIterator::Next() {
   if (opportunity_iter_ == opportunities_.end())
     return NGLayoutOpportunity();
   auto* opportunity = opportunity_iter_;
   opportunity_iter_++;
   return NGLayoutOpportunity(*opportunity);
 }
 
 }  // namespace blink