asList() always returns a new instance

[reneky]

It would be nice if it created the immutable List on the first call, so that it can be used for Angular Dart @input

[davidmorgan]

Thanks for the suggestion.

Does it not work to use the BuiltList directly? It is Iterable, after all.

We wouldn't want to add a field to BuiltList just for this as it would be trading memory in every case to support an occasional use case. An alternative implementation would be to use an "expando".