*   `tf.cond` emits a StatelessIf op if the branch functions are stateless and
    do not touch any resources.
*   `tf.cond`, `tf.while` and `if` and `while` in AutoGraph now accept a
    nonscalar predicate if has a single element. This does not affect non-V2
    control flow.
*   `tf.while_loop` emits a StatelessWhile op if the cond and body functions are
    stateless and do not touch any resources.