CPUs.

## Major Features And Improvements

*   New Optimizer internal API for non-slot variables. Descendants of
    AdamOptimizer that access _beta[12]_power will need to be updated.
*   `tf.estimator.{FinalExporter,LatestExporter}` now export stripped
    SavedModels. This improves forward compatibility of the SavedModel.
*   FFT support added to XLA CPU/GPU.