Add virtual destructors to IntersectionObserverCallback

third_party/WebKit/Source/core/dom/IntersectionObservation.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/IntersectionObservation.h"
 
 #include "core/dom/ElementRareData.h"
 #include "core/dom/IntersectionObserver.h"
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutText.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/PaintLayer.h"
 
 namespace blink {
 
 IntersectionObservation::IntersectionObservation(IntersectionObserver& observer, Element& target, bool shouldReportRootBounds)
     : m_observer(observer)
     , m_target(target.ensureIntersectionObserverData().createWeakPtr(&target))
     , m_active(true)
     , m_shouldReportRootBounds(shouldReportRootBounds)
     , m_lastThresholdIndex(0)
 {
 }
 
+IntersectionObservation::~IntersectionObservation()
+{
+}
+
 Element* IntersectionObservation::target() const
 {
     return toElement(m_target.get());
 }
 
 void IntersectionObservation::initializeGeometry(IntersectionGeometry& geometry)
 {
     ASSERT(m_target);
     LayoutObject* targetLayoutObject = target()->layoutObject();
     if (targetLayoutObject->isBoxModelObject())
@@ skipping 131 matching lines @@
     m_observer.clear();
 }
 
 DEFINE_TRACE(IntersectionObservation)
 {
     visitor->trace(m_observer);
     visitor->trace(m_target);
 }
 
 } // namespace blink