Stop re-signaling a slotchange event

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 291 matching lines @@
   if (m_oldDistributedNodes != m_distributedNodes) {
     for (auto& node : m_oldDistributedNodes)
       node->lazyReattachIfAttached();
     for (auto& node : m_distributedNodes)
       node->lazyReattachIfAttached();
     InspectorInstrumentation::didPerformSlotDistribution(this);
   }
   m_oldDistributedNodes.clear();
 }
 
-void HTMLSlotElement::enqueueSlotChangeEvent() {
-  if (!m_slotchangeEventEnqueued) {
-    Microtask::enqueueMicrotask(WTF::bind(
-        &HTMLSlotElement::dispatchSlotChangeEvent, wrapPersistent(this)));
-    m_slotchangeEventEnqueued = true;
-  }
-
+void HTMLSlotElement::didSlotChange(SlotChangeType slotChangeType) {
+  if (slotChangeType == SlotChangeType::Initial)
+    enqueueSlotChangeEvent();
   ShadowRoot* root = containingShadowRoot();
   DCHECK(root);
   DCHECK(root->isV1());
   root->owner()->setNeedsDistributionRecalc();
   // Check slotchange recursively since this slotchange may cause another
   // slotchange.
-  checkSlotChange();
+  checkSlotChange(SlotChangeType::Chained);
+}
+
+void HTMLSlotElement::enqueueSlotChangeEvent() {
+  if (m_slotchangeEventEnqueued)
+    return;
+  Microtask::enqueueMicrotask(WTF::bind(
+      &HTMLSlotElement::dispatchSlotChangeEvent, wrapPersistent(this)));
+  m_slotchangeEventEnqueued = true;
 }
 
 bool HTMLSlotElement::hasAssignedNodesSlow() const {
   ShadowRoot* root = containingShadowRoot();
   DCHECK(root);
   DCHECK(root->isV1());
   SlotAssignment& assignment = root->ensureSlotAssignment();
   if (assignment.findSlotByName(name()) != this)
     return false;
   return assignment.findHostChildBySlotName(name());
@@ skipping 13 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