--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -46,16 +46,17 @@
 
 #include "gfxContext.h"
 #include "gfxUserFontSet.h"
 #include "nsContentList.h"
 #include "nsPresContext.h"
 #include "nsIContent.h"
 #include "mozilla/dom/BrowserBridgeChild.h"
 #include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/CanonicalBrowsingContext.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/PointerEventHandler.h"
 #include "mozilla/dom/PopupBlocker.h"
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/DocumentInlines.h"
 #include "mozilla/dom/UserActivation.h"
 #include "nsAnimationManager.h"
 #include "nsNameSpaceManager.h"  // for Pref-related rule management (bugs 22963,20760,31816)
@@ -6546,31 +6547,48 @@ already_AddRefed<nsIContent> PresShell::
     fm->GetFocusedElementForWindow(mDocument->GetWindow(), false, nullptr,
                                    getter_AddRefs(focusedElement));
     return focusedElement.forget();
   }
   return nullptr;
 }
 
 already_AddRefed<PresShell> PresShell::GetParentPresShellForEventHandling() {
-  NS_ENSURE_TRUE(mPresContext, nullptr);
+  if (!mPresContext) {
+    return nullptr;
+  }
 
   // Now, find the parent pres shell and send the event there
-  nsCOMPtr<nsIDocShellTreeItem> treeItem = mPresContext->GetDocShell();
-  if (!treeItem) {
-    treeItem = mForwardingContainer.get();
+  RefPtr<nsDocShell> docShell = mPresContext->GetDocShell();
+  if (!docShell) {
+    docShell = mForwardingContainer.get();
   }
 
   // Might have gone away, or never been around to start with
-  NS_ENSURE_TRUE(treeItem, nullptr);
-
-  nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
-  treeItem->GetInProcessParent(getter_AddRefs(parentTreeItem));
-  nsCOMPtr<nsIDocShell> parentDocShell = do_QueryInterface(parentTreeItem);
-  NS_ENSURE_TRUE(parentDocShell && treeItem != parentTreeItem, nullptr);
+  if (!docShell) {
+    return nullptr;
+  }
+
+  BrowsingContext* bc = docShell->GetBrowsingContext();
+  if (!bc) {
+    return nullptr;
+  }
+
+  RefPtr<BrowsingContext> parentBC;
+  if (XRE_IsParentProcess()) {
+    parentBC = bc->Canonical()->GetParentCrossChromeBoundary();
+  } else {
+    parentBC = bc->GetParent();
+  }
+
+  RefPtr<nsIDocShell> parentDocShell =
+      parentBC ? parentBC->GetDocShell() : nullptr;
+  if (!parentDocShell) {
+    return nullptr;
+  }
 
   RefPtr<PresShell> parentPresShell = parentDocShell->GetPresShell();
   return parentPresShell.forget();
 }
 
 nsresult PresShell::EventHandler::RetargetEventToParent(
     WidgetGUIEvent* aGUIEvent, nsEventStatus* aEventStatus) {
   // Send this events straight up to the parent pres shell.