IntersectionObserver: use nullptr for implicit root.

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

Index: third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h
diff --git a/third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h b/third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h
deleted file mode 100644
index 0bf1dc041dbee5fe4b6e8662bb466f0eb5e5f9df..0000000000000000000000000000000000000000
--- a/third_party/WebKit/Source/core/dom/NodeIntersectionObserverData.h
+++ /dev/null
@@ -1,44 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// 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
-
-#include "bindings/core/v8/ScriptWrappable.h"
-#include "bindings/core/v8/TraceWrapperMember.h"
-#include "platform/heap/Handle.h"
-
-namespace blink {
-
-class Node;
-class IntersectionObservation;
-class IntersectionObserver;
-
-class NodeIntersectionObserverData
-    : public GarbageCollected<NodeIntersectionObserverData>,
-      public TraceWrapperBase {
- public:
-  NodeIntersectionObserverData();
-
-  IntersectionObservation* getObservationFor(IntersectionObserver&);
-  void addObservation(IntersectionObservation&);
-  void removeObservation(IntersectionObserver&);
-  void activateValidIntersectionObservers(Node&);
-  void deactivateAllIntersectionObservers(Node&);
-
-  DECLARE_TRACE();
-  DECLARE_TRACE_WRAPPERS();
-
- private:
-  // IntersectionObservers for which the Node owning this data is root.
-  HeapHashSet<WeakMember<IntersectionObserver>> m_intersectionObservers;
-  // IntersectionObservations for which the Node owning this data is target.
-  HeapHashMap<TraceWrapperMember<IntersectionObserver>,
-              Member<IntersectionObservation>>
-      m_intersectionObservations;
-};
-
-}  // namespace blink
-
-#endif  // NodeIntersectionObserverData_h