Mac a11y: Report actual window as window instead of top level widget

Bug: 948878
Change-Id: I79ef6f31524cb6cbca7acab42f5b488e1b2d9524
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1849123Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704309}

ui/views/accessibility/view_ax_platform_node_delegate_mac.mm

@@ -27,12 +27,8 @@ gfx::NativeViewAccessible ViewAXPlatformNodeDelegateMac::GetNSWindow() {
   if (!widget)
     return nil;
 
-  auto* top_level_widget = widget->GetTopLevelWidget();
-  if (!top_level_widget)
-    return nil;
-
   auto* window_host = NativeWidgetMacNSWindowHost::GetFromNativeWindow(
-      top_level_widget->GetNativeWindow());
+      widget->GetNativeWindow());
   if (!window_host)
     return nil;