https://github.com/flutter/flutter/blob/fa063eb4ce4140dec9a887c3130239c68f7b713e/examples/api/lib/material/refresh_indicator/refresh_indicator.1.dart uses shrinkWrap, but really it shouldn't. Unfortunately, it is currently hard to achieve this effect without shrinkWrapping. We should implement whatever additional Slivers are needed to not require shrinkWrapping here (e.g. SliverDecoration).