IntersectionObserver: use nullptr for implicit root.

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

 // 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.
 
-#include "core/dom/NodeIntersectionObserverData.h"
+#include "core/dom/ElementIntersectionObserverData.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/IntersectionObservation.h"
 #include "core/dom/IntersectionObserver.h"
 #include "core/dom/IntersectionObserverController.h"
 
 namespace blink {
 
-NodeIntersectionObserverData::NodeIntersectionObserverData() {}
+ElementIntersectionObserverData::ElementIntersectionObserverData() {}
 
-IntersectionObservation* NodeIntersectionObserverData::getObservationFor(
+IntersectionObservation* ElementIntersectionObserverData::getObservationFor(
     IntersectionObserver& observer) {
   auto i = m_intersectionObservations.find(&observer);
   if (i == m_intersectionObservations.end())
     return nullptr;
   return i->value;
 }
 
-void NodeIntersectionObserverData::addObservation(
+void ElementIntersectionObserverData::addObserver(
+    IntersectionObserver& observer) {
+  m_intersectionObservers.add(&observer);
+}
+
+void ElementIntersectionObserverData::removeObserver(
+    IntersectionObserver& observer) {
+  m_intersectionObservers.remove(&observer);
+}
+
+void ElementIntersectionObserverData::addObservation(
     IntersectionObservation& observation) {
   m_intersectionObservations.add(
       TraceWrapperMember<IntersectionObserver>(this, &observation.observer()),
       &observation);
 }
 
-void NodeIntersectionObserverData::removeObservation(
+void ElementIntersectionObserverData::removeObservation(
     IntersectionObserver& observer) {
   m_intersectionObservations.remove(&observer);
 }
 
-void NodeIntersectionObserverData::activateValidIntersectionObservers(
+void ElementIntersectionObserverData::activateValidIntersectionObservers(
     Node& node) {
-  IntersectionObserverController& controller =
-      node.document().ensureIntersectionObserverController();
-  for (auto& observer : m_intersectionObservers)
-    controller.addTrackedObserver(*observer);
+  for (auto& observer : m_intersectionObservers) {
+    observer->trackingDocument()
+        .ensureIntersectionObserverController()
+        .addTrackedObserver(*observer);
+  }
 }
 
-void NodeIntersectionObserverData::deactivateAllIntersectionObservers(
+void ElementIntersectionObserverData::deactivateAllIntersectionObservers(
     Node& node) {
+  for (auto& observer : m_intersectionObservers) {
+    observer->trackingDocument()
+        .ensureIntersectionObserverController()
+        .addTrackedObserver(*observer);
+  }
   node.document()
       .ensureIntersectionObserverController()
       .removeTrackedObserversForRoot(node);
 }
 
-DEFINE_TRACE(NodeIntersectionObserverData) {
+DEFINE_TRACE(ElementIntersectionObserverData) {
   visitor->trace(m_intersectionObservers);
   visitor->trace(m_intersectionObservations);
 }
 
-DEFINE_TRACE_WRAPPERS(NodeIntersectionObserverData) {
+DEFINE_TRACE_WRAPPERS(ElementIntersectionObserverData) {
   for (auto& entry : m_intersectionObservations) {
     visitor->traceWrappers(entry.key);
   }
 }
 
 }  // namespace blink