Do not allocate SlotAssignment unless a shadowroot has a slot

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

 // 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.
 
 #ifndef SlotAssignment_h
 #define SlotAssignment_h
 
 // #include "core/dom/DocumentOrderedList.h"
 #include "core/dom/DocumentOrderedMap.h"
 #include "platform/heap/Handle.h"
@@ skipping 24 matching lines @@
   //    void assignSlot(const Node& slottable);
   // 2. https://dom.spec.whatwg.org/#assign-slotables
   //    void assignSlotables(HTMLSlotElement&);
   // As an optimization, Blink does not implement these literally.
   // Instead, provide alternative, HTMLSlotElement::hasAssignedNodesSlow()
   // so that slotchange can be detected.
 
   void resolveDistribution();
   const HeapVector<Member<HTMLSlotElement>>& slots();
 
-  void slotAdded(HTMLSlotElement&);
+  void didAddSlot(HTMLSlotElement&);
   void slotRemoved(HTMLSlotElement&);
   void slotRenamed(const AtomicString& oldName, HTMLSlotElement&);
-  void hostChildSlotNameChanged(const AtomicString& oldValue,
-                                const AtomicString& newValue);
+  void didChangeHostChildSlotName(const AtomicString& oldValue,
+                                  const AtomicString& newValue);
 
   bool findHostChildBySlotName(const AtomicString& slotName) const;
 
   DECLARE_TRACE();
 
  private:
   explicit SlotAssignment(ShadowRoot& owner);
 
   void collectSlots();
 
   void resolveAssignment();
   void distributeTo(Node&, HTMLSlotElement&);
 
   HeapVector<Member<HTMLSlotElement>> m_slots;
   Member<DocumentOrderedMap> m_slotMap;
   WeakMember<ShadowRoot> m_owner;
   unsigned m_needsCollectSlots : 1;
   unsigned m_slotCount : 31;
 };
 
 }  // namespace blink
 
 #endif  // HTMLSlotAssignment_h