Do not use outdated m_distributedNodes of slots in non-shadow trees

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

 /*
  * 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 79 matching lines @@
       child = NodeTraversal::next(*child, this);
     } else {
       m_distributedNodes.append(child);
       child = NodeTraversal::nextSkippingChildren(*child, this);
     }
   }
 }
 
 const HeapVector<Member<Node>>& HTMLSlotElement::getDistributedNodes() {
   DCHECK(!needsDistributionRecalc());
+  // m_distributedNodes of slots in non-shadow trees are not updated in recalc
+  // distribution flow.
   if (!supportsDistribution())
     updateDistributedNodesManually();
   return m_distributedNodes;
 }
 
 void HTMLSlotElement::appendAssignedNode(Node& hostChild) {
   DCHECK(hostChild.isSlotable());
   m_assignedNodes.append(&hostChild);
 }
 
@@ skipping 61 matching lines @@
   if (index == 0)
     return nullptr;
   return m_distributedNodes[index - 1].get();
 }
 
 AtomicString HTMLSlotElement::name() const {
   return normalizeSlotName(fastGetAttribute(HTMLNames::nameAttr));
 }
 
 void HTMLSlotElement::attachLayoutTree(const AttachContext& context) {
-  for (auto& node : m_distributedNodes) {
+  for (auto& node : getDistributedNodes()) {
     if (node->needsAttach())
       node->attachLayoutTree(context);
   }
 
   HTMLElement::attachLayoutTree(context);
 }
 
 void HTMLSlotElement::detachLayoutTree(const AttachContext& context) {
   for (auto& node : m_distributedNodes)
     node->lazyReattachIfAttached();
@@ skipping 118 matching lines @@
 }
 
 void HTMLSlotElement::enqueueSlotChangeEvent() {
   if (!m_slotchangeEventEnqueued) {
     Microtask::enqueueMicrotask(WTF::bind(
         &HTMLSlotElement::dispatchSlotChangeEvent, wrapPersistent(this)));
     m_slotchangeEventEnqueued = true;
   }
 
   ShadowRoot* root = containingShadowRoot();
+  // TODO(hayato): Relax this check if slots in non-shadow trees are well
+  // supported.
   DCHECK(root);
   DCHECK(root->isV1());
   root->owner()->setNeedsDistributionRecalc();
   // Check slotchange recursively since this slotchange may cause another
   // slotchange.
   checkSlotChange();
 }
 
 bool HTMLSlotElement::hasAssignedNodesSlow() const {
   ShadowRoot* root = containingShadowRoot();
@@ skipping 19 matching lines @@
 
 DEFINE_TRACE(HTMLSlotElement) {
   visitor->trace(m_assignedNodes);
   visitor->trace(m_distributedNodes);
   visitor->trace(m_oldDistributedNodes);
   visitor->trace(m_distributedIndices);
   HTMLElement::trace(visitor);
 }
 
 }  // namespace blink