IntersectionObserver: send notifications when objects disappear.

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/frame/LocalFrame.h"
@@ skipping 125 matching lines @@
         descendant = descendant->containingBlock();
     return descendant;
 }
 
 bool IntersectionObservation::computeGeometry(IntersectionGeometry& geometry) const
 {
     // In the first few lines here, before initializeGeometry is called, "return true"
     // effectively means "if the previous observed state was that root and target were
     // intersecting, then generate a notification indicating that they are no longer
     // intersecting."  This happens, for example, when root or target is removed from the
-    // DOM tree and not reinserted before the next frame is generated.
+    // DOM tree and not reinserted before the next frame is generated, or display:none
+    // is set on the root or target.
     Element* targetElement = target();
     if (!targetElement)
         return false;
     if (!targetElement->inShadowIncludingDocument())
         return true;
     DCHECK(m_observer);
     Element* rootElement = m_observer->root();
     if (rootElement && !rootElement->inShadowIncludingDocument())
         return true;
 
     LayoutObject* rootLayoutObject = m_observer->rootLayoutObject();
     if (!rootLayoutObject || !rootLayoutObject->isBoxModelObject())
-        return false;
+        return true;
     // TODO(szager): Support SVG
     LayoutObject* targetLayoutObject = targetElement->layoutObject();
     if (!targetLayoutObject)
-        return false;
+        return true;
     if (!targetLayoutObject->isBoxModelObject() && !targetLayoutObject->isText())
-        return false;
+        return true;
     if (!isContainingBlockChainDescendant(targetLayoutObject, rootLayoutObject))
         return true;
 
     initializeGeometry(geometry);
 
     clipToRoot(geometry);
 
     mapTargetRectToTargetFrameCoordinates(geometry.targetRect);
 
     if (geometry.doesIntersect)
@@ skipping 67 matching lines @@
     m_observer.clear();
 }
 
 DEFINE_TRACE(IntersectionObservation)
 {
     visitor->trace(m_observer);
     visitor->trace(m_target);
 }
 
 } // namespace blink