b/170458334

This can be repro'ed using the sample at: https://flutter.dev/docs/cookbook/forms/retrieve-input

Add maxLength: 5 to the TextField widget and try entering: "123456789" to the text field. You will need to press backspace 5 times to start deleting the text. My hunch is that we are not storing the inner "cursor position" correctly. The data seems to be correct (pressing the FAB always returns 12345).

I recall this used to work so marking as regression.