1 files changed, 15 insertions, 8 deletions
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index ac9601caf..e779c060c 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1736,8 +1736,6 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INTERNAL(nsDocument)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOnDemandBuiltInUASheets)
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPreloadingImages)
 
-  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mIntersectionObservers)
-
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSubImportLinks)
 
   for (uint32_t i = 0; i < tmp->mFrameRequestCallbacks.Length(); ++i) {
@@ -12375,15 +12373,15 @@ nsDocument::ReportUseCounters()
 void
 nsDocument::AddIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  NS_ASSERTION(mIntersectionObservers.IndexOf(aObserver) == nsTArray<int>::NoIndex,
-               "Intersection observer already in the list");
-  mIntersectionObservers.AppendElement(aObserver);
+  MOZ_ASSERT(!mIntersectionObservers.Contains(aObserver),
+             "Intersection observer already in the list");
+  mIntersectionObservers.PutEntry(aObserver);
 }
 
 void
 nsDocument::RemoveIntersectionObserver(DOMIntersectionObserver* aObserver)
 {
-  mIntersectionObservers.RemoveElement(aObserver);
+  mIntersectionObservers.RemoveEntry(aObserver);
 }
 
 void
@@ -12396,7 +12394,8 @@ nsDocument::UpdateIntersectionObservations()
       time = perf->Now();
     }
   }
-  for (const auto& observer : mIntersectionObservers) {
+  for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Get()->GetKey();
     observer->Update(this, time);
   }
 }
@@ -12404,6 +12403,10 @@ nsDocument::UpdateIntersectionObservations()
 void
 nsDocument::ScheduleIntersectionObserverNotification()
 {
+  if (mIntersectionObservers.IsEmpty()) {
+    return;
+  }
+
   nsCOMPtr<nsIRunnable> notification = NewRunnableMethod(this,
     &nsDocument::NotifyIntersectionObservers);
   NS_DispatchToCurrentThread(notification);
@@ -12412,7 +12415,11 @@ nsDocument::ScheduleIntersectionObserverNotification()
 void
 nsDocument::NotifyIntersectionObservers()
 {
-  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers);
+  nsTArray<RefPtr<DOMIntersectionObserver>> observers(mIntersectionObservers.Count());
+  for (auto iter = mIntersectionObservers.Iter(); !iter.Done(); iter.Next()) {
+    DOMIntersectionObserver* observer = iter.Get()->GetKey();
+    observers.AppendElement(observer);
+  }
   for (const auto& observer : observers) {
     observer->Notify();
   }