[LayoutNG] Initial NGLayoutOpportunityIterator implementation

third_party/WebKit/Source/core/layout/ng/ng_physical_constraint_space.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_physical_constraint_space.h"
 
 #include "core/layout/LayoutBox.h"
 #include "core/style/ComputedStyle.h"
 
 namespace blink {
@@ skipping 27 matching lines @@
       width_direction_fragmentation_type_(
           other.width_direction_fragmentation_type_),
       height_direction_fragmentation_type_(
           other.height_direction_fragmentation_type_) {}
 
 void NGPhysicalConstraintSpace::AddExclusion(const NGExclusion,
                                              unsigned options) {
   // TODO(layout-ng): Implement.
 }
 
-DoublyLinkedList<const NGExclusion> NGPhysicalConstraintSpace::Exclusions(
-    unsigned options) const {
-  DoublyLinkedList<const NGExclusion> exclusions;
-  // TODO(layout-ng): Implement.
-  return exclusions;
+const DoublyLinkedList<const NGExclusion>*
+NGPhysicalConstraintSpace::Exclusions(unsigned options) const {
+  // TODO(layout-ng): Filter based on options? Perhaps layout Opportunities
+  // should filter instead?
+  return &exclusions_;
 }
 
 }  // namespace blink