chromeos: Makes mushrome use simplified display management

services/ui/ws/window_server.cc

Index: services/ui/ws/window_server.cc
diff --git a/services/ui/ws/window_server.cc b/services/ui/ws/window_server.cc
index d012b886dc2f0bc50ecc2246398ff6bcdc5aef36..2a5278215fe494f197705aeea8c52e8fb298a2b5 100644
--- a/services/ui/ws/window_server.cc
+++ b/services/ui/ws/window_server.cc
@@ -826,7 +826,13 @@ void WindowServer::OnSurfaceCreated(const cc::SurfaceInfo& surface_info) {
     window_paint_callback_.Run(window);
 
   auto* display = display_manager_->GetDisplayContaining(window);
-  if (display && window == display->GetActiveRootWindow()) {
+  WindowManagerDisplayRoot* display_root =
+      display ? display->GetActiveWindowManagerDisplayRoot() : nullptr;
+  if (display_root && (window == display_root->root() ||
+                       (!display_root->window_manager_state()
+                             ->window_tree()
+                             ->automatically_create_display_roots() &&
+                        window->parent() == display_root->root()))) {
     // A new surface for a WindowManager root has been created. This is a
     // special case because ServerWindows created by the WindowServer are not
     // part of a WindowTree. Send the SurfaceId directly to FrameGenerator and