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

third_party/WebKit/Source/core/dom/IntersectionObserverController.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/IntersectionObserverController.h"
 
 #include "core/dom/Document.h"
 
 namespace blink {
 
@@ skipping 55 matching lines @@
         if (observer->hasEntries())
             scheduleIntersectionObserverForDelivery(*observer);
     }
 }
 
 void IntersectionObserverController::addTrackedObserver(IntersectionObserver& observer)
 {
     m_trackedIntersectionObservers.add(&observer);
 }
 
-void IntersectionObserverController::removeTrackedObserversForRoot(const Element& root)
+void IntersectionObserverController::removeTrackedObserversForRoot(const Node& root)
 {
     HeapVector<Member<IntersectionObserver>> toRemove;
     for (auto& observer : m_trackedIntersectionObservers) {
         if (observer->root() == &root)
             toRemove.append(observer);
     }
     m_trackedIntersectionObservers.removeAll(toRemove);
 }
 
 DEFINE_TRACE(IntersectionObserverController)
 {
     visitor->trace(m_trackedIntersectionObservers);
     visitor->trace(m_pendingIntersectionObservers);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink