--- a/layout/generic/nsSubDocumentFrame.cpp
+++ b/layout/generic/nsSubDocumentFrame.cpp
@@ -442,22 +442,16 @@ nsSubDocumentFrame::BuildDisplayList(nsD
       constructZoomItem ||
       haveDisplayPort ||
       presContext->IsRootContentDocument() ||
       (sf && sf->IsScrollingActive(aBuilder)))
   {
     needsOwnLayer = true;
   }
 
-  if (!needsOwnLayer && aBuilder->IsBuildingLayerEventRegions() &&
-      nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(presShell))
-  {
-    needsOwnLayer = true;
-  }
-
   if (aBuilder->IsRetainingDisplayList()) {
     // The value of needsOwnLayer can change between builds without
     // an invalidation recorded for this frame (like if the root
     // scrollframe becomes active). If this happens,
     // then we need to notify the builder so that merging can
     // happen correctly.
     if (!mPreviouslyNeededLayer ||
         mPreviouslyNeededLayer.value() != needsOwnLayer) {
@@ -500,17 +494,21 @@ nsSubDocumentFrame::BuildDisplayList(nsD
     if (subdocRootFrame) {
       nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();
       nsDisplayListBuilder::AutoCurrentScrollParentIdSetter idSetter(
           aBuilder,
           ignoreViewportScrolling && rootScrollFrame && rootScrollFrame->GetContent()
               ? nsLayoutUtils::FindOrCreateIDFor(rootScrollFrame->GetContent())
               : aBuilder->GetCurrentScrollParentId());
 
-      aBuilder->SetAncestorHasApzAwareEventHandler(false);
+      bool hasDocumentLevelListenersForApzAwareEvents =
+          aBuilder->IsBuildingLayerEventRegions() &&
+          nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(presShell);
+
+      aBuilder->SetAncestorHasApzAwareEventHandler(hasDocumentLevelListenersForApzAwareEvents);
       subdocRootFrame->
         BuildDisplayListForStackingContext(aBuilder, &childItems);
     }
 
     if (!aBuilder->IsForEventDelivery()) {
       // If we are going to use a displayzoom below then any items we put under
       // it need to have underlying frames from the subdocument. So we need to
       // calculate the bounds based on which frame will be the underlying frame

--- a/layout/painting/nsDisplayList.cpp
+++ b/layout/painting/nsDisplayList.cpp
@@ -6856,45 +6856,31 @@ nsDisplaySubDocument::nsDisplaySubDocume
                                            nsSubDocumentFrame* aSubDocFrame,
                                            nsDisplayList* aList, uint32_t aFlags)
     : nsDisplayOwnLayer(aBuilder, aFrame, aList, aBuilder->CurrentActiveScrolledRoot(), aFlags)
     , mScrollParentId(aBuilder->GetCurrentScrollParentId())
     , mShouldFlatten(false)
     , mSubDocFrame(aSubDocFrame)
 {
   MOZ_COUNT_CTOR(nsDisplaySubDocument);
-  mForceDispatchToContentRegion =
-    aBuilder->IsBuildingLayerEventRegions() &&
-    nsLayoutUtils::HasDocumentLevelListenersForApzAwareEvents(aFrame->PresShell());
 
   // The SubDocument display item is conceptually outside the viewport frame,
   // so in cases where the viewport frame is an AGR, the SubDocument's AGR
   // should be not the viewport frame itself, but its parent AGR.
   if (*mAnimatedGeometryRoot == mFrame && mAnimatedGeometryRoot->mParentAGR) {
     mAnimatedGeometryRoot = mAnimatedGeometryRoot->mParentAGR;
   }
 }
 
 #ifdef NS_BUILD_REFCNT_LOGGING
 nsDisplaySubDocument::~nsDisplaySubDocument() {
   MOZ_COUNT_DTOR(nsDisplaySubDocument);
 }
 #endif
 
-already_AddRefed<Layer>
-nsDisplaySubDocument::BuildLayer(nsDisplayListBuilder* aBuilder,
-                                 LayerManager* aManager,
-                                 const ContainerLayerParameters& aContainerParameters) {
-  RefPtr<Layer> layer = nsDisplayOwnLayer::BuildLayer(aBuilder, aManager, aContainerParameters);
-  layer->AsContainerLayer()->SetEventRegionsOverride(mForceDispatchToContentRegion
-    ? EventRegionsOverride::ForceDispatchToContent
-    : EventRegionsOverride::NoOverride);
-  return layer.forget();
-}
-
 UniquePtr<ScrollMetadata>
 nsDisplaySubDocument::ComputeScrollMetadata(LayerManager* aLayerManager,
                                             const ContainerLayerParameters& aContainerParameters)
 {
   if (!(mFlags & GENERATE_SCROLLABLE_LAYER)) {
     return UniquePtr<ScrollMetadata>(nullptr);
   }
 

--- a/layout/painting/nsDisplayList.h
+++ b/layout/painting/nsDisplayList.h
@@ -5106,20 +5106,16 @@ class nsDisplaySubDocument : public nsDi
 public:
   nsDisplaySubDocument(nsDisplayListBuilder* aBuilder,
                        nsIFrame* aFrame, nsSubDocumentFrame* aSubDocFrame,
                        nsDisplayList* aList, uint32_t aFlags);
 #ifdef NS_BUILD_REFCNT_LOGGING
   virtual ~nsDisplaySubDocument();
 #endif
 
-  virtual already_AddRefed<Layer> BuildLayer(nsDisplayListBuilder* aBuilder,
-                                             LayerManager* aManager,
-                                             const ContainerLayerParameters& aContainerParameters) override;
-
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder,
                            bool* aSnap) const override;
 
   virtual nsSubDocumentFrame* SubDocumentFrame() { return mSubDocFrame; }
 
   virtual bool ComputeVisibility(nsDisplayListBuilder* aBuilder,
                                  nsRegion* aVisibleRegion) override;