--- a/dom/base/nsDocument.h
+++ b/dom/base/nsDocument.h
@@ -615,16 +615,20 @@ public:
 
   virtual void AddIntersectionObserver(
     mozilla::dom::DOMIntersectionObserver* aObserver) override;
   virtual void RemoveIntersectionObserver(
     mozilla::dom::DOMIntersectionObserver* aObserver) override;
   virtual void UpdateIntersectionObservations() override;
   virtual void ScheduleIntersectionObserverNotification() override;
   virtual void NotifyIntersectionObservers() override;
+  virtual bool HasIntersectionObservers() const override
+  {
+    return !mIntersectionObservers.IsEmpty();
+  }
 
   virtual void NotifyLayerManagerRecreated() override;
 
   virtual void ScheduleSVGForPresAttrEvaluation(nsSVGElement* aSVG) override;
   virtual void UnscheduleSVGForPresAttrEvaluation(nsSVGElement* aSVG) override;
   virtual void ResolveScheduledSVGPresAttrs() override;
   bool IsSynthesized();
 

--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -3115,16 +3115,17 @@ public:
   virtual void AddIntersectionObserver(
     mozilla::dom::DOMIntersectionObserver* aObserver) = 0;
   virtual void RemoveIntersectionObserver(
     mozilla::dom::DOMIntersectionObserver* aObserver) = 0;
 
   virtual void UpdateIntersectionObservations() = 0;
   virtual void ScheduleIntersectionObserverNotification() = 0;
   virtual void NotifyIntersectionObservers() = 0;
+  virtual bool HasIntersectionObservers() const = 0;
 
   // Dispatch a runnable related to the document.
   virtual nsresult Dispatch(mozilla::TaskCategory aCategory,
                             already_AddRefed<nsIRunnable>&& aRunnable) override;
 
   virtual nsISerialEventTarget*
   EventTargetFor(mozilla::TaskCategory aCategory) const override;
 

--- a/layout/base/nsRefreshDriver.cpp
+++ b/layout/base/nsRefreshDriver.cpp
@@ -1583,16 +1583,38 @@ CollectDocuments(nsIDocument* aDocument,
 {
   static_cast<AutoTArray<nsCOMPtr<nsIDocument>, 32>*>(aDocArray)->
     AppendElement(aDocument);
   aDocument->EnumerateSubDocuments(CollectDocuments, aDocArray);
   return true;
 }
 
 void
+nsRefreshDriver::UpdateIntersectionObservations()
+{
+  AutoTArray<nsCOMPtr<nsIDocument>, 32> documents;
+
+  if (mPresContext->Document()->HasIntersectionObservers()) {
+    documents.AppendElement(mPresContext->Document());
+  }
+
+  mPresContext->Document()->CollectDescendantDocuments(
+    documents,
+    [](const nsIDocument* document) -> bool {
+      return document->HasIntersectionObservers();
+    });
+
+  for (uint32_t i = 0; i < documents.Length(); ++i) {
+    nsIDocument* doc = documents[i];
+    doc->UpdateIntersectionObservations();
+    doc->ScheduleIntersectionObserverNotification();
+  }
+}
+
+void
 nsRefreshDriver::DispatchAnimationEvents()
 {
   if (!mPresContext) {
     return;
   }
 
   AutoTArray<nsCOMPtr<nsIDocument>, 32> documents;
   CollectDocuments(mPresContext->Document(), &documents);
@@ -1950,23 +1972,17 @@ nsRefreshDriver::Tick(int64_t aNowEpoch,
   // Update any popups that may need to be moved or hidden due to their
   // anchor changing.
   nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
   if (pm) {
     pm->UpdatePopupPositions(this);
   }
 #endif
 
-  AutoTArray<nsCOMPtr<nsIDocument>, 32> documents;
-  CollectDocuments(mPresContext->Document(), &documents);
-  for (uint32_t i = 0; i < documents.Length(); ++i) {
-    nsIDocument* doc = documents[i];
-    doc->UpdateIntersectionObservations();
-    doc->ScheduleIntersectionObserverNotification();
-  }
+  UpdateIntersectionObservations();
 
   /*
    * Perform notification to imgIRequests subscribed to listen
    * for refresh events.
    */
 
   for (auto iter = mStartTable.Iter(); !iter.Done(); iter.Next()) {
     const uint32_t& delay = iter.Key();

--- a/layout/base/nsRefreshDriver.h
+++ b/layout/base/nsRefreshDriver.h
@@ -380,16 +380,17 @@ private:
     mozilla::Maybe<mozilla::TimeStamp> mStartTime;
     RequestTable mEntries;
   };
   typedef nsClassHashtable<nsUint32HashKey, ImageStartData> ImageStartTable;
 
   void DispatchPendingEvents();
   void DispatchAnimationEvents();
   void RunFrameRequestCallbacks(mozilla::TimeStamp aNowTime);
+  void UpdateIntersectionObservations();
   void Tick(int64_t aNowEpoch, mozilla::TimeStamp aNowTime);
 
   enum EnsureTimerStartedFlags {
     eNone = 0,
     eForceAdjustTimer = 1 << 0,
     eAllowTimeToGoBackwards = 1 << 1,
     eNeverAdjustTimer = 1 << 2,
   };