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

components/mus/ws/window_tree_client_unittest.cc

Index: components/mus/ws/window_tree_client_unittest.cc
diff --git a/components/mus/ws/window_tree_client_unittest.cc b/components/mus/ws/window_tree_client_unittest.cc
index d3d5f776549ed00208e73a56e9367ad934c1a2fe..3c2d3e8a164b1609d29f956c6e2cbfe02b171efc 100644
--- a/components/mus/ws/window_tree_client_unittest.cc
+++ b/components/mus/ws/window_tree_client_unittest.cc
@@ -276,6 +276,7 @@ class TestWindowTreeClientImpl : public mojom::WindowTreeClient,
   void OnEmbed(ClientSpecificId client_id,
                WindowDataPtr root,
                mojom::WindowTreePtr tree,
+               int64_t display_id,
                Id focused_window_id,
                bool drawn) override {
     // TODO(sky): add coverage of |focused_window_id|.
@@ -296,6 +297,7 @@ class TestWindowTreeClientImpl : public mojom::WindowTreeClient,
   }
   void OnTopLevelCreated(uint32_t change_id,
                          mojom::WindowDataPtr data,
+                         int64_t display_id,
                          bool drawn) override {
     tracker()->OnTopLevelCreated(change_id, std::move(data), drawn);
   }