mus-ws: Plumb FrameSinkId to Children

ash/mus/window_manager_unittest.cc

Index: ash/mus/window_manager_unittest.cc
diff --git a/ash/mus/window_manager_unittest.cc b/ash/mus/window_manager_unittest.cc
index 4fb7e82a5a81e1b71ee1a7f5d9b90b0ab3c5a8c6..84f23a499b81003297ff774a10e3f3a7a62a4fdc 100644
--- a/ash/mus/window_manager_unittest.cc
+++ b/ash/mus/window_manager_unittest.cc
@@ -99,7 +99,8 @@ TEST_F(MusWindowManagerTest, OpenWindow) {
   properties[ui::mojom::WindowManager::kWindowType_InitProperty] =
       mojo::ConvertTo<std::vector<uint8_t>>(
           static_cast<int32_t>(ui::mojom::WindowType::WINDOW));
-  aura::WindowTreeHostMus window_tree_host_mus(&client, &properties);
+  aura::WindowTreeHostMus window_tree_host_mus(&client, cc::FrameSinkId(),
+                                               &properties);
   window_tree_host_mus.InitHost();
   aura::Window* child_window = new aura::Window(nullptr);
   child_window->Init(ui::LAYER_NOT_DRAWN);