IntersectionObserver: use nullptr for implicit root.

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 3635b9b0180081041d5b80f061a2a4a92addb803..bdbc7ff408eebbbd32c1cc7a9f4722444077cd47 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -93,7 +93,6 @@
 #include "core/dom/NodeChildRemovalTracker.h"
 #include "core/dom/NodeComputedStyle.h"
 #include "core/dom/NodeFilter.h"
-#include "core/dom/NodeIntersectionObserverData.h"
 #include "core/dom/NodeIterator.h"
 #include "core/dom/NodeRareData.h"
 #include "core/dom/NodeTraversal.h"
@@ -5718,12 +5717,6 @@ Document::ensureIntersectionObserverController() {
   return *m_intersectionObserverController;
 }
 
-NodeIntersectionObserverData& Document::ensureIntersectionObserverData() {
-  if (!m_intersectionObserverData)
-    m_intersectionObserverData = new NodeIntersectionObserverData();
-  return *m_intersectionObserverData;
-}
-
 ResizeObserverController& Document::ensureResizeObserverController() {
   if (!m_resizeObserverController)
     m_resizeObserverController = new ResizeObserverController();
@@ -6529,7 +6522,6 @@ DEFINE_TRACE(Document) {
   visitor->trace(m_contextDocument);
   visitor->trace(m_canvasFontCache);
   visitor->trace(m_intersectionObserverController);
-  visitor->trace(m_intersectionObserverData);
   visitor->trace(m_snapCoordinator);
   visitor->trace(m_resizeObserverController);
   visitor->trace(m_propertyRegistry);