[IntersectionObserver] Remove hack for on-stack wrapper tracing

The hack is no longer necessary. Also remove some other obsolete
TODO's.

BUG=796145
R=yukishiino@chromium.org

Change-Id: Ie84e143759d8e882f7403da48da6f882a962998a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1760984Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688494}

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

@@ -46,9 +46,6 @@ void IntersectionObservation::Compute(unsigned flags) {
     return;
   if (!(flags & kIgnoreDelay) &&
       timestamp - last_run_time_ < observer_->GetEffectiveDelay()) {
-    // TODO(crbug.com/915495): Need to eventually notify the observer of the
-    // updated intersection because there's currently nothing to guarantee this
-    // Compute() method will be called again after the delay period has passed.
     return;
   }
   if (target_->isConnected() && Observer()->trackVisibility()) {

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

@@ -25,9 +25,6 @@ IntersectionObserverController::~IntersectionObserverController() = default;
 
 void IntersectionObserverController::PostTaskToDeliverObservations() {
   DCHECK(GetExecutionContext());
-  // TODO(ojan): These tasks decide whether to throttle a subframe, so they
-  // need to be unthrottled, but we should throttle all the other tasks
-  // (e.g. ones coming from the web page).
   GetExecutionContext()
       ->GetTaskRunner(TaskType::kInternalIntersectionObserver)
       ->PostTask(
@@ -53,18 +50,15 @@ void IntersectionObserverController::DeliverIntersectionObservations(
     pending_intersection_observers_.clear();
     return;
   }
-  // TODO(yukishiino): Remove this CHECK once https://crbug.com/809784 gets
-  // resolved.
-  CHECK(!context->IsContextDestroyed());
+  HeapVector<Member<IntersectionObserver>> intersection_observers_being_invoked;
   for (auto& observer : pending_intersection_observers_) {
     if (observer->GetDeliveryBehavior() == behavior)
-      intersection_observers_being_invoked_.push_back(observer);
+      intersection_observers_being_invoked.push_back(observer);
   }
-  for (auto& observer : intersection_observers_being_invoked_) {
+  for (auto& observer : intersection_observers_being_invoked) {
     pending_intersection_observers_.erase(observer);
     observer->Deliver();
   }
-  intersection_observers_being_invoked_.clear();
 }
 
 bool IntersectionObserverController::ComputeTrackedIntersectionObservations(
@@ -111,7 +105,6 @@ void IntersectionObserverController::RemoveTrackedTarget(Element& target) {
 void IntersectionObserverController::Trace(blink::Visitor* visitor) {
   visitor->Trace(tracked_observation_targets_);
   visitor->Trace(pending_intersection_observers_);
-  visitor->Trace(intersection_observers_being_invoked_);
   ContextClient::Trace(visitor);
 }
 

third_party/blink/renderer/core/intersection_observer/intersection_observer_controller.h

@@ -65,10 +65,6 @@ class IntersectionObserverController
   // IntersectionObservers for which this is the execution context of the
   // callback.
   HeapHashSet<Member<IntersectionObserver>> pending_intersection_observers_;
-  // TODO(https://crbug.com/796145): Remove this hack once on-stack objects
-  // get supported by either of wrapper-tracing or unified GC.
-  HeapVector<Member<IntersectionObserver>>
-      intersection_observers_being_invoked_;
   // This is 'true' if any tracked observation target is being tracked by an
   // observer for which observer->trackVisibility() is true.
   bool needs_occlusion_tracking_;