Fix assignedNodes({flatten:true}) to return fallback content in document tree

third_party/WebKit/Source/core/html/HTMLSlotElement.h

 /*
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 90 matching lines @@
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   HTMLSlotElement(Document&);
 
   InsertionNotificationRequest InsertedInto(ContainerNode*) final;
   void RemovedFrom(ContainerNode*) final;
   void WillRecalcStyle(StyleRecalcChange) final;
 
+  const HeapVector<Member<Node>> GetDistributedNodesWithFallback() const;
+
   void EnqueueSlotChangeEvent();
 
   HeapVector<Member<Node>> assigned_nodes_;
   HeapVector<Member<Node>> distributed_nodes_;
   HeapVector<Member<Node>> old_distributed_nodes_;
   HeapHashMap<Member<const Node>, size_t> distributed_indices_;
   bool slotchange_event_enqueued_ = false;
 };
 
 }  // namespace blink
 
 #endif  // HTMLSlotElement_h