Aura-Mus: Allocate a LocalSurfaceId on size change

ui/aura/test/mus/test_window_tree.cc

Index: ui/aura/test/mus/test_window_tree.cc
diff --git a/ui/aura/test/mus/test_window_tree.cc b/ui/aura/test/mus/test_window_tree.cc
index 37d551cf986f7e26181578d4ad122503925f152d..603d61ae3693d9fca56f8dff8bd05cf89f6f4842 100644
--- a/ui/aura/test/mus/test_window_tree.cc
+++ b/ui/aura/test/mus/test_window_tree.cc
@@ -138,6 +138,8 @@ void TestWindowTree::SetWindowBounds(
     uint32_t window_id,
     const gfx::Rect& bounds,
     const base::Optional<cc::LocalSurfaceId>& local_surface_id) {
+  window_id_ = window_id;
+  last_local_surface_id_ = local_surface_id;
   OnChangeReceived(change_id, WindowTreeChangeType::BOUNDS);
 }