Bug 986347 - Restore accidentaly removed HasBogusPopupsDropShadowOnMultiMonitor() call. r=jimm

widget/windows/nsWindow.cpp

@@ -494,7 +494,8 @@ nsWindow::Create(nsIWidget *aParent,
       parent = nullptr;
     }
 
-    if (IsVistaOrLater() && !IsWin8OrLater()) {
+    if (IsVistaOrLater() && !IsWin8OrLater() &&
+        HasBogusPopupsDropShadowOnMultiMonitor()) {
       extendedStyle |= WS_EX_COMPOSITED;
     }