Use Document, rather than document element, for implicit root.

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

 /*
  * Copyright (C) 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2008 David Smith <catfish.man@gmail.com>
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef ElementRareData_h
 #define ElementRareData_h
 
 #include "core/animation/ElementAnimations.h"
 #include "core/dom/Attr.h"
 #include "core/dom/CompositorProxiedPropertySet.h"
 #include "core/dom/DatasetDOMStringMap.h"
-#include "core/dom/ElementIntersectionObserverData.h"
 #include "core/dom/NamedNodeMap.h"
+#include "core/dom/NodeIntersectionObserverData.h"
 #include "core/dom/NodeRareData.h"
 #include "core/dom/PseudoElement.h"
 #include "core/dom/custom/CustomElementDefinition.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/html/ClassList.h"
 #include "core/style/StyleInheritedData.h"
 #include "platform/heap/Handle.h"
 #include "wtf/HashSet.h"
 #include "wtf/OwnPtr.h"
 
@@ skipping 77 matching lines @@
     void decrementCompositorProxiedProperties(uint32_t properties);
     CompositorProxiedPropertySet* proxiedPropertyCounts() const { return m_proxiedProperties.get(); }
 
     void setCustomElementDefinition(PassRefPtrWillBeRawPtr<CustomElementDefinition> definition) { m_customElementDefinition = definition; }
     CustomElementDefinition* customElementDefinition() const { return m_customElementDefinition.get(); }
 
     AttrNodeList& ensureAttrNodeList();
     AttrNodeList* attrNodeList() { return m_attrNodeList.get(); }
     void removeAttrNodeList() { m_attrNodeList.clear(); }
 
-    ElementIntersectionObserverData* intersectionObserverData() const { return m_intersectionObserverData.get(); }
-    ElementIntersectionObserverData& ensureIntersectionObserverData()
+    NodeIntersectionObserverData* intersectionObserverData() const { return m_intersectionObserverData.get(); }
+    NodeIntersectionObserverData& ensureIntersectionObserverData()
     {
         if (!m_intersectionObserverData)
-            m_intersectionObserverData = new ElementIntersectionObserverData();
+            m_intersectionObserverData = new NodeIntersectionObserverData();
         return *m_intersectionObserverData;
     }
 
     DECLARE_TRACE_AFTER_DISPATCH();
 
 private:
     CompositorProxiedPropertySet& ensureCompositorProxiedPropertySet();
     void clearCompositorProxiedPropertySet() { m_proxiedProperties = nullptr; }
 
     short m_tabindex;
 
     LayoutSize m_minimumSizeForResizing;
     IntSize m_savedLayerScrollOffset;
 
     OwnPtrWillBeMember<DatasetDOMStringMap> m_dataset;
     OwnPtrWillBeMember<ClassList> m_classList;
     OwnPtrWillBeMember<ElementShadow> m_shadow;
     OwnPtrWillBeMember<NamedNodeMap> m_attributeMap;
     OwnPtrWillBeMember<AttrNodeList> m_attrNodeList;
     OwnPtrWillBeMember<InlineCSSStyleDeclaration> m_cssomWrapper;
     OwnPtr<CompositorProxiedPropertySet> m_proxiedProperties;
 
     PersistentWillBeMember<ElementAnimations> m_elementAnimations;
-    PersistentWillBeMember<ElementIntersectionObserverData> m_intersectionObserverData;
+    PersistentWillBeMember<NodeIntersectionObserverData> m_intersectionObserverData;
 
     RefPtr<ComputedStyle> m_computedStyle;
     RefPtrWillBeMember<CustomElementDefinition> m_customElementDefinition;
 
     RefPtrWillBeMember<PseudoElement> m_generatedBefore;
     RefPtrWillBeMember<PseudoElement> m_generatedAfter;
     RefPtrWillBeMember<PseudoElement> m_generatedFirstLetter;
     RefPtrWillBeMember<PseudoElement> m_backdrop;
 
     explicit ElementRareData(LayoutObject*);
@@ skipping 99 matching lines @@
 inline CompositorProxiedPropertySet& ElementRareData::ensureCompositorProxiedPropertySet()
 {
     if (!m_proxiedProperties)
         m_proxiedProperties = CompositorProxiedPropertySet::create();
     return *m_proxiedProperties;
 }
 
 } // namespace
 
 #endif // ElementRareData_h