Do not allocate SlotAssignment unless a shadowroot has a slot

third_party/WebKit/Source/core/dom/shadow/SlotAssignment.cpp

 // Copyright 2015 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/dom/shadow/SlotAssignment.h"
 
 #include "core/HTMLNames.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/Node.h"
 #include "core/dom/NodeTraversal.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/InsertionPoint.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/html/HTMLSlotElement.h"
 
 namespace blink {
 
-void SlotAssignment::slotAdded(HTMLSlotElement& slot) {
+void SlotAssignment::didAddSlot(HTMLSlotElement& slot) {
   // Relevant DOM Standard:
   // https://dom.spec.whatwg.org/#concept-node-insert
   // 6.4:  Run assign slotables for a tree with node's tree and a set containing
   // each inclusive descendant of node that is a slot.
 
   ++m_slotCount;
   m_needsCollectSlots = true;
 
   if (!m_slotMap->contains(slot.name())) {
     m_slotMap->add(slot.name(), &slot);
@@ skipping 54 matching lines @@
 
   m_slotMap->remove(oldSlotName, &slot);
   m_slotMap->add(slot.name(), &slot);
 
   bool hasAssignedNodesAfter = slot.hasAssignedNodesSlow();
 
   if (hasAssignedNodesBefore || hasAssignedNodesAfter)
     slot.didSlotChange(SlotChangeType::Initial);
 }
 
-void SlotAssignment::hostChildSlotNameChanged(const AtomicString& oldValue,
-                                              const AtomicString& newValue) {
+void SlotAssignment::didChangeHostChildSlotName(const AtomicString& oldValue,
+                                                const AtomicString& newValue) {
   if (HTMLSlotElement* slot =
           findSlotByName(HTMLSlotElement::normalizeSlotName(oldValue))) {
     slot->didSlotChange(SlotChangeType::Initial);
     m_owner->owner()->setNeedsDistributionRecalc();
   }
   if (HTMLSlotElement* slot =
           findSlotByName(HTMLSlotElement::normalizeSlotName(newValue))) {
     slot->didSlotChange(SlotChangeType::Initial);
     m_owner->owner()->setNeedsDistributionRecalc();
   }
@@ skipping 71 matching lines @@
   DCHECK_EQ(m_slots.size(), m_slotCount);
 }
 
 DEFINE_TRACE(SlotAssignment) {
   visitor->trace(m_slots);
   visitor->trace(m_slotMap);
   visitor->trace(m_owner);
 }
 
 }  // namespace blink