IntersectionObserver: use nullptr for implicit root.

third_party/WebKit/Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003-2011, 2013, 2014 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 43 matching lines @@
 class DOMStringMap;
 class DOMTokenList;
 class ElementRareData;
 class ElementShadow;
 class ExceptionState;
 class Image;
 class InputDeviceCapabilities;
 class Locale;
 class MutableStylePropertySet;
 class NamedNodeMap;
-class NodeIntersectionObserverData;
+class ElementIntersectionObserverData;
 class PseudoElement;
 class ResizeObservation;
 class ResizeObserver;
 class ScrollState;
 class ScrollStateCallback;
 class ScrollToOptions;
 class ShadowRoot;
 class ShadowRootInit;
 class StylePropertySet;
 class StylePropertyMap;
@@ skipping 635 matching lines @@
       const QualifiedName& attributeName,
       const AtomicString& oldValue,
       const AtomicString& newValue);
 
   DECLARE_VIRTUAL_TRACE();
 
   DECLARE_VIRTUAL_TRACE_WRAPPERS();
 
   SpellcheckAttributeState spellcheckAttributeState() const;
 
-  NodeIntersectionObserverData* intersectionObserverData() const;
-  NodeIntersectionObserverData& ensureIntersectionObserverData();
+  ElementIntersectionObserverData* intersectionObserverData() const;
+  ElementIntersectionObserverData& ensureIntersectionObserverData();
 
   HeapHashMap<Member<ResizeObserver>, Member<ResizeObservation>>*
   resizeObserverData() const;
   HeapHashMap<Member<ResizeObserver>, Member<ResizeObservation>>&
   ensureResizeObserverData();
   void setNeedsResizeObserverUpdate();
 
  protected:
   Element(const QualifiedName& tagName, Document*, ConstructionType);
 
@@ skipping 442 matching lines @@
 #define DECLARE_ELEMENT_FACTORY_WITH_TAGNAME(T) \
   static T* create(const QualifiedName&, Document&)
 #define DEFINE_ELEMENT_FACTORY_WITH_TAGNAME(T)                     \
   T* T::create(const QualifiedName& tagName, Document& document) { \
     return new T(tagName, document);                               \
   }
 
 }  // namespace blink
 
 #endif  // Element_h