Allows menu host windows to be enumerated in DragTargetWindowFinder

ui/views/widget/desktop_aura/x11_desktop_handler.cc

Index: ui/views/widget/desktop_aura/x11_desktop_handler.cc
diff --git a/ui/views/widget/desktop_aura/x11_desktop_handler.cc b/ui/views/widget/desktop_aura/x11_desktop_handler.cc
index d98dfa644354d2590d7e42c20e4eb52eaa68fdd2..de968b2a6378250190dcd06f543ce23cc11b9845 100644
--- a/ui/views/widget/desktop_aura/x11_desktop_handler.cc
+++ b/ui/views/widget/desktop_aura/x11_desktop_handler.cc
@@ -165,6 +165,20 @@ uint32_t X11DesktopHandler::Dispatch(const base::NativeEvent& event) {
       }
       break;
     }
+    // Menus created by Chrome can be Drag and Drop targets. Since they are
+    // direct children of the screen root window and have override_redirect
+    // we cannot use regular _NET_CLIENT_LIST_STACKING property to find them
+    // and therefore use a separate cache to keep track of them.
+    case CreateNotify: {
+      XCreateWindowEvent *xcwe = &event->xcreatewindow;
+      ui::XMenuList::GetInstance()->MaybeRegisterMenu(xcwe->window);
+      break;
+    }
+    case DestroyNotify: {
+      XDestroyWindowEvent *xdwe = &event->xdestroywindow;
+      ui::XMenuList::GetInstance()->MaybeUnregisterMenu(xdwe->window);
+      break;
+    }
   }
 
   return POST_DISPATCH_NONE;