[IntersectionObserver] Speculative fix for bad cast

These are instances where we don't actually need to remove an element from its
tracking document's IntersectionObserverController, because it wasn't being
tracked anyway.

BUG=1007334,1006957

Change-Id: Ia14165402e2a3774a180d0215145d3d46338942c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1828358
Commit-Queue: Stefan Zager <szager@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700896}

third_party/blink/renderer/core/dom/element.cc

@@ -2657,10 +2657,11 @@ void Element::RemovedFrom(ContainerNode& insertion_point) {
     if (ElementAnimations* element_animations = data->GetElementAnimations())
       element_animations->CssAnimations().Cancel();
 
-    if (data->IntersectionObserverData()) {
+    if (was_in_document && data->IntersectionObserverData()) {
       data->IntersectionObserverData()->ComputeIntersectionsForTarget(
           IntersectionObservation::kExplicitRootObserversNeedUpdate |
-          IntersectionObservation::kImplicitRootObserversNeedUpdate);
+          IntersectionObservation::kImplicitRootObserversNeedUpdate |
+          IntersectionObservation::kIgnoreDelay);
       GetDocument().EnsureIntersectionObserverController().RemoveTrackedElement(
           *this);
     }

third_party/blink/renderer/core/intersection_observer/intersection_observation.cc

@@ -70,7 +70,11 @@ void IntersectionObservation::Disconnect() {
     ElementIntersectionObserverData* observer_data =
         target_->IntersectionObserverData();
     observer_data->RemoveObservation(*Observer());
-    if (target_->isConnected() &&
+    // We track connected elements that are either the root of an explicit root
+    // observer, or the target of an implicit root observer. If the target was
+    // previously being tracked, but no longer needs to be tracked, then remove
+    // it.
+    if (target_->isConnected() && Observer()->RootIsImplicit() &&
         !observer_data->IsTargetOfImplicitRootObserver() &&
         !observer_data->IsRoot()) {
       IntersectionObserverController* controller =

third_party/blink/renderer/core/intersection_observer/intersection_observer.cc

@@ -318,7 +318,8 @@ void IntersectionObserver::observe(Element* target,
     // be recorded after observe() is called, even if the target is detached.
     observation->ComputeIntersection(
         IntersectionObservation::kImplicitRootObserversNeedUpdate |
-        IntersectionObservation::kExplicitRootObserversNeedUpdate);
+        IntersectionObservation::kExplicitRootObserversNeedUpdate |
+        IntersectionObservation::kIgnoreDelay);
   }
 }