Fix bug in keeping capture in sync during destruction

ui/aura/test/mus/window_tree_client_private.cc

Index: ui/aura/test/mus/window_tree_client_private.cc
diff --git a/ui/aura/test/mus/window_tree_client_private.cc b/ui/aura/test/mus/window_tree_client_private.cc
index 666ae69b6102194524dd36a6b516f8045fc70266..d3c8a0f92f1c255322dedf4c8cb667a77e45a397 100644
--- a/ui/aura/test/mus/window_tree_client_private.cc
+++ b/ui/aura/test/mus/window_tree_client_private.cc
@@ -66,7 +66,7 @@ void WindowTreeClientPrivate::CallOnCaptureChanged(Window* new_capture,
 void WindowTreeClientPrivate::SetTreeAndClientId(
     ui::mojom::WindowTree* window_tree,
     ClientSpecificId client_id) {
-  tree_client_impl_->tree_ = window_tree;
+  tree_client_impl_->WindowTreeConnectionEstablished(window_tree);
   tree_client_impl_->client_id_ = client_id;
 }