Remove unnecessary override of Node#cloneNode in ShadowRoot's WebIDL

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

 /*
  * Copyright (C) 2011 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.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 122 matching lines @@
   void didChangeHostChildSlotName(const AtomicString& oldValue,
                                   const AtomicString& newValue);
 
   void distributeV1();
 
   Element* activeElement() const;
 
   String innerHTML() const;
   void setInnerHTML(const String&, ExceptionState& = ASSERT_NO_EXCEPTION);
 
-  Node* cloneNode(bool, ExceptionState&);
+  Node* cloneNode(bool, ExceptionState&) override;
 
   void setDelegatesFocus(bool flag) { m_delegatesFocus = flag; }
   bool delegatesFocus() const { return m_delegatesFocus; }
 
   bool containsShadowRoots() const { return m_childShadowRootCount; }
 
   StyleSheetList& styleSheets();
   void setStyleSheets(StyleSheetList* styleSheetList) {
     m_styleSheetList = styleSheetList;
     ScriptWrappableVisitor::writeBarrier(this, m_styleSheetList);
@@ skipping 11 matching lines @@
   ShadowRootRareDataV0& ensureShadowRootRareDataV0();
   SlotAssignment& ensureSlotAssignment();
 
   void addChildShadowRoot() { ++m_childShadowRootCount; }
   void removeChildShadowRoot() {
     DCHECK_GT(m_childShadowRootCount, 0u);
     --m_childShadowRootCount;
   }
   void invalidateDescendantInsertionPoints();
 
-  // ShadowRoots should never be cloned.
-  Node* cloneNode(bool) override { return nullptr; }
-
   Member<ShadowRootRareDataV0> m_shadowRootRareDataV0;
   Member<StyleSheetList> m_styleSheetList;
   Member<SlotAssignment> m_slotAssignment;
   unsigned m_childShadowRootCount : 13;
   unsigned m_type : 2;
   unsigned m_registeredWithParentShadowRoot : 1;
   unsigned m_descendantInsertionPointsIsValid : 1;
   unsigned m_delegatesFocus : 1;
 };
 
@@ skipping 14 matching lines @@
                   treeScope,
                   treeScope->rootNode().isShadowRoot(),
                   treeScope.rootNode().isShadowRoot());
 DEFINE_TYPE_CASTS(TreeScope, ShadowRoot, shadowRoot, true, true);
 
 CORE_EXPORT std::ostream& operator<<(std::ostream&, const ShadowRootType&);
 
 }  // namespace blink
 
 #endif  // ShadowRoot_h