I think ultimately this depends on what kind of selection control you're using, so it's not really platform-dependant. Even in `TextField`'s implementation you can override `textSelectionControl` so it's still up to the developer.

Anyways IMO we should deprecate this callback and let the `TextSelectionControl` implementation decides how the handles should be built and what interactions it should support. Currently it does not have enough information (as it doesn't have access to the `EditableTextState` that builds the selection overlay).