[X11] Don't return closed windows from GetAcceleratedWidgetAtScreenPoint

This issue can manifest when quickly dragging tabs on tiling window
managers.

Bug: None
Change-Id: Ib160ce88b7fb4e3801489511f9b4433bbfe7d291
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6176746
Commit-Queue: Maksim Sisov <msisov@igalia.com>
Reviewed-by: Maksim Sisov <msisov@igalia.com>
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1407147}

ui/ozone/platform/x11/x11_screen_ozone.cc

@@ -162,8 +162,15 @@ gfx::AcceleratedWidget X11ScreenOzone::GetAcceleratedWidgetAtScreenPoint(
     const gfx::Point& point) const {
   gfx::Point point_in_pixels =
       gfx::ToFlooredPoint(PointDipToPx(GetAllDisplays(), point));
-  return static_cast<gfx::AcceleratedWidget>(
+  auto widget = static_cast<gfx::AcceleratedWidget>(
       x11::GetWindowAtPoint(point_in_pixels));
+  auto* window = window_manager_->GetWindow(widget);
+  if (window && !window->IsVisible()) {
+    // The window cache may be out of sync with respect to recently changed
+    // window state. This can happen if the window was recently hidden.
+    return gfx::kNullAcceleratedWidget;
+  }
+  return widget;
 }
 
 gfx::AcceleratedWidget X11ScreenOzone::GetLocalProcessWidgetAtPoint(