Revert "[impeller] Remove declare_undefined_values (#37829)" (#37831)
Revert "[impeller] Remove declare_undefined_values (#37829)" (#37831)

This reverts commit c3645c3b89471c1c22ab414be9b98234173b9558.
flutter/engine,flutter/engine,flutter/engine,flutter/engine,flutter/engine,flutter/engine,flutter/engine,flutter/engine