Bug 1656107 - remove FindContentForSubDocument use from EventStateManager. r=farre

Differential Revision: https://phabricator.services.mozilla.com/D98617

dom/events/EventStateManager.cpp

@@ -4501,8 +4501,9 @@ void EventStateManager::NotifyMouseOver(WidgetMouseEvent* aMouseEvent,
   // content associated with our subdocument.
   EnsureDocument(mPresContext);
   if (Document* parentDoc = mDocument->GetInProcessParentDocument()) {
-    if (nsCOMPtr<nsIContent> docContent =
+    if (RefPtr<BrowsingContext> bc = mDocument->GetBrowsingContext()) {
-            parentDoc->FindContentForSubDocument(mDocument)) {
+      if (!bc->IsCached()) {
+        if (nsCOMPtr<nsIContent> docContent = bc->GetEmbedderElement()) {
           if (PresShell* parentPresShell = parentDoc->GetPresShell()) {
             RefPtr<EventStateManager> parentESM =
                 parentPresShell->GetPresContext()->EventStateManager();
@@ -4510,6 +4511,8 @@ void EventStateManager::NotifyMouseOver(WidgetMouseEvent* aMouseEvent,
           }
         }
       }
+    }
+  }
   // Firing the DOM event in the parent document could cause all kinds
   // of havoc.  Reverify and take care.
   if (wrapper->mLastOverElement == aContent) return;