setWithSave(Object newValue, CallContext ctx) Set a value, but return cookie so old value can be restored.
This is intended for fluid-let where (in the case of multiple threads)
a simple save-restore isn't always the right thing.
Set a value, but return cookie so old value can be restored.
This is intended for fluid-let where (in the case of multiple threads)
a simple save-restore isn't always the right thing.