Handle modified displays in mustash.

services/ui/ws/window_tree.cc

Index: services/ui/ws/window_tree.cc
diff --git a/services/ui/ws/window_tree.cc b/services/ui/ws/window_tree.cc
index 9a99c46247d728c2c067b90a236bd52b880dd6f4..bf86c98c62e53f7f9b2d959c11da8ba0e5221112 100644
--- a/services/ui/ws/window_tree.cc
+++ b/services/ui/ws/window_tree.cc
@@ -219,6 +219,10 @@ void WindowTree::OnWindowDestroyingTreeImpl(WindowTree* tree) {
   }
 }
 
+void WindowTree::OnWmDisplayModified(const display::Display& display) {
+  window_manager_internal_->WmDisplayModified(display);
+}
+
 void WindowTree::NotifyChangeCompleted(
     uint32_t change_id,
     mojom::WindowManagerErrorCode error_code) {