mus: Changes SetDisplayRoot() to create actual display

services/ui/ws/window_server_delegate.cc

Index: services/ui/ws/window_server_delegate.cc
diff --git a/services/ui/ws/window_server_delegate.cc b/services/ui/ws/window_server_delegate.cc
index 6d1194b7fb7b463ae8d2e40d190ea3f62923ca7f..1250bade481fb812b592a6458c9e29150acb24a7 100644
--- a/services/ui/ws/window_server_delegate.cc
+++ b/services/ui/ws/window_server_delegate.cc
@@ -21,5 +21,8 @@ WindowServerDelegate::CreateWindowTreeBinding(
   return nullptr;
 }
 
+void WindowServerDelegate::OnWillCreateTreeForWindowManager(
+    bool automatically_create_display_roots) {}
+
 }  // namespace ws
 }  // namespace ui