Bug 827976 - Improve usage of the hidden window for nsXULWindow::Destroy. r=aklotz

Differential Revision: https://phabricator.services.mozilla.com/D21075

--HG--
extra : moz-landing-system : lando

Author: felipc

xpfe/appshell/nsXULWindow.cpp

@@ -462,19 +462,28 @@ NS_IMETHODIMP nsXULWindow::Destroy() {
   if (parent) {
     nsCOMPtr<nsIWidget> parentWidget;
     parent->GetMainWidget(getter_AddRefs(parentWidget));
-    if (!parentWidget || parentWidget->IsVisible()) {
-      nsCOMPtr<nsIBaseWindow> baseHiddenWindow;
+
+    if (parentWidget && parentWidget->IsVisible()) {
+      bool isParentHiddenWindow = false;
+
       if (appShell) {
-        nsCOMPtr<nsIXULWindow> hiddenWindow;
-        appShell->GetHiddenWindow(getter_AddRefs(hiddenWindow));
-        if (hiddenWindow) baseHiddenWindow = do_GetInterface(hiddenWindow);
+        bool hasHiddenWindow = false;
+        appShell->GetHasHiddenWindow(&hasHiddenWindow);
+        if (hasHiddenWindow) {
+          nsCOMPtr<nsIBaseWindow> baseHiddenWindow;
+          nsCOMPtr<nsIXULWindow> hiddenWindow;
+          appShell->GetHiddenWindow(getter_AddRefs(hiddenWindow));
+          if (hiddenWindow) {
+            baseHiddenWindow = do_GetInterface(hiddenWindow);
+            isParentHiddenWindow = (baseHiddenWindow == parent);
+          }
+        }
       }
+
       // somebody screwed up somewhere. hiddenwindow shouldn't be anybody's
       // parent. still, when it happens, skip activating it.
-      if (baseHiddenWindow != parent) {
-        nsCOMPtr<nsIWidget> parentWidget;
-        parent->GetMainWidget(getter_AddRefs(parentWidget));
-        if (parentWidget) parentWidget->PlaceBehind(eZPlacementTop, 0, true);
+      if (!isParentHiddenWindow) {
+        parentWidget->PlaceBehind(eZPlacementTop, 0, true);
       }
     }
   }