Combine 2 exclusions in Layout Opportunity Tree if they shadow each other

third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_tree_node.h

Index: third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_tree_node.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_tree_node.h b/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_tree_node.h
index 6e2c913b6db0183d521b75d459f548bb528ee63c..037768f7aec805c08696d732d1bcb84b20de2106 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_tree_node.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_tree_node.h
@@ -16,7 +16,7 @@ namespace blink {
 // layout opportunity after the parent spatial rectangle is split by the
 // exclusion rectangle.
 struct CORE_EXPORT NGLayoutOpportunityTreeNode
-    : public GarbageCollected<NGLayoutOpportunityTreeNode> {
+    : public GarbageCollectedFinalized<NGLayoutOpportunityTreeNode> {
  public:
   // Default constructor.
   // Creates a Layout Opportunity tree node that is limited by it's own edge
@@ -41,15 +41,31 @@ struct CORE_EXPORT NGLayoutOpportunityTreeNode
   // Edge that limits this layout opportunity from above.
   NGEdge exclusion_edge;
 
-  // Exclusion that splits apart this layout opportunity.
-  const NGExclusion* exclusion;  // Not owned.
+  // Exclusions that splits apart this layout opportunity.
+  Vector<const NGExclusion*> exclusions;  // Not owned.
+
+  // Exclusion that represent all combined exclusions that
+  // split this node.
+  std::unique_ptr<NGExclusion> combined_exclusion;
 
   // Whether this node is a leaf node.
-  // The node is a leaf if it doesn't have an exclusion that splits it apart.
-  bool IsLeafNode() const { return !exclusion; }
+  // The node is a leaf if it doesn't have exclusions that split it apart.
+  bool IsLeafNode() const { return exclusions.isEmpty(); }
+
+  String ToString() const;
 
   DECLARE_TRACE();
 };
 
+inline std::ostream& operator<<(std::ostream& stream,
+                                const NGLayoutOpportunityTreeNode& value) {
+  return stream << value.ToString();
+}
+
+inline std::ostream& operator<<(std::ostream& out,
+                                const NGLayoutOpportunityTreeNode* value) {
+  return out << (value ? value->ToString() : "(null)");
+}
+
 }  // namespace blink
 #endif  // NGLayoutOpportunityTreeNode_h