Adds ability for WindowManager to create display roots

services/ui/ws/display_binding.cc

Index: services/ui/ws/display_binding.cc
diff --git a/services/ui/ws/display_binding.cc b/services/ui/ws/display_binding.cc
index f70c92bf01e3031ec7875de3567bb1217e893704..09157038fb09f1208a37a93e3bf2af3b94d46da4 100644
--- a/services/ui/ws/display_binding.cc
+++ b/services/ui/ws/display_binding.cc
@@ -31,7 +31,8 @@ WindowTree* DisplayBindingImpl::CreateWindowTree(ServerWindow* root) {
   WindowTree* tree = window_server_->EmbedAtWindow(
       root, user_id_, std::move(client_), embed_flags,
       base::WrapUnique(new WindowManagerAccessPolicy));
-  tree->ConfigureWindowManager();
+  const bool automatically_create_display_roots = true;
+  tree->ConfigureWindowManager(automatically_create_display_roots);
   return tree;
 }