mus: Send display-id to client only for the root windows.

components/mus/ws/test_utils.h

Index: components/mus/ws/test_utils.h
diff --git a/components/mus/ws/test_utils.h b/components/mus/ws/test_utils.h
index 67c5da771654197aebfd70b8a472b73fa056bd02..ba6ce9b8742b9ed0a8d1b54cfa91d67e1974b4d9 100644
--- a/components/mus/ws/test_utils.h
+++ b/components/mus/ws/test_utils.h
@@ -277,6 +277,7 @@ class TestWindowTreeClient : public mus::mojom::WindowTreeClient {
   void OnEmbed(uint16_t client_id,
                mojom::WindowDataPtr root,
                mus::mojom::WindowTreePtr tree,
+               int64_t display_id,
                Id focused_window_id,
                bool drawn) override;
   void OnEmbeddedAppDisconnected(uint32_t window) override;
@@ -284,6 +285,7 @@ class TestWindowTreeClient : public mus::mojom::WindowTreeClient {
   void OnLostCapture(Id window_id) override;
   void OnTopLevelCreated(uint32_t change_id,
                          mojom::WindowDataPtr data,
+                         int64_t display_id,
                          bool drawn) override;
   void OnWindowBoundsChanged(uint32_t window,
                              mojo::RectPtr old_bounds,