Rewrite IntersectionObserver list handling to be more robust.

Tag mcp-graveyard/UXP%935.

1 files changed, 15 insertions, 3 deletions

diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index 14de65cbd..d4d488379 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -12313,6 +12313,10 @@ nsDocument::RemoveIntersectionObserver(DOMIntersectionObserver* aObserver)
 void
 nsDocument::UpdateIntersectionObservations()
 {
+  if (mIntersectionObservers.IsEmpty()) {
+    return;
+  }
+
   DOMHighResTimeStamp time = 0;
   if (nsPIDOMWindowInner* window = GetInnerWindow()) {
     Performance* perf = window->GetPerformance();
@@ -12320,9 +12324,15 @@ nsDocument::UpdateIntersectionObservations()
       time = perf->Now();
     }
   }
+  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers.Count());
   for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
     DOMIntersectionObserver* observer = iter.Get()->GetKey();
-    observer->Update(this, time);
+    observers.AppendElement(observer);
+  }
+  for (const auto& observer : observers) {
+    if (observer) {
+      observer->Update(this, time);
+    }
   }
 }
 
@@ -12335,7 +12345,7 @@ nsDocument::ScheduleIntersectionObserverNotification()
 
   nsCOMPtr<nsIRunnable> notification = NewRunnableMethod(this,
     &nsDocument::NotifyIntersectionObservers);
-  NS_DispatchToCurrentThread(notification);
+  NS_DispatchToCurrentThread(notification.forget());
 }
 
 void
@@ -12347,7 +12357,9 @@ nsDocument::NotifyIntersectionObservers()
     observers.AppendElement(observer);
   }
   for (const auto& observer : observers) {
-    observer->Notify();
+    if (observer) {
+      observer->Notify();
+    }
   }
 }