IntersectionObserver: use nullptr for implicit root.

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

Index: third_party/WebKit/Source/core/dom/ElementIntersectionObserverData.h
diff --git a/third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h b/third_party/WebKit/Source/core/dom/ElementIntersectionObserverData.h
similarity index 76%
rename from third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h
rename to third_party/WebKit/Source/core/dom/ElementIntersectionObserverData.h
index 0bf1dc041dbee5fe4b6e8662bb466f0eb5e5f9df..e9647e95e633a487dd9ad7d91f39af74171edc9e 100644
--- a/third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h
+++ b/third_party/WebKit/Source/core/dom/ElementIntersectionObserverData.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef NodeIntersectionObserverData_h
-#define NodeIntersectionObserverData_h
+#ifndef ElementIntersectionObserverData_h
+#define ElementIntersectionObserverData_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "bindings/core/v8/TraceWrapperMember.h"
@@ -15,13 +15,15 @@ class Node;
 class IntersectionObservation;
 class IntersectionObserver;
 
-class NodeIntersectionObserverData
-    : public GarbageCollected<NodeIntersectionObserverData>,
+class ElementIntersectionObserverData
+    : public GarbageCollected<ElementIntersectionObserverData>,
       public TraceWrapperBase {
  public:
-  NodeIntersectionObserverData();
+  ElementIntersectionObserverData();
 
   IntersectionObservation* getObservationFor(IntersectionObserver&);
+  void addObserver(IntersectionObserver&);
+  void removeObserver(IntersectionObserver&);
   void addObservation(IntersectionObservation&);
   void removeObservation(IntersectionObserver&);
   void activateValidIntersectionObservers(Node&);
@@ -41,4 +43,4 @@ class NodeIntersectionObserverData
 
 }  // namespace blink
 
-#endif  // NodeIntersectionObserverData_h
+#endif  // ElementIntersectionObserverData_h