*   <THIS SECTION SHOULD CONTAIN API, ABI AND BEHAVIORAL BREAKING CHANGES>

*   `tf.summary.trace_on` now takes a `profiler_outdir` argument. This must be
    set if `profiler` arg is set to `True`.

    *   `tf.summary.trace_export`'s `profiler_outdir` arg is now a no-op.
        Enabling the profiler now requires setting `profiler_outdir` in
        `trace_on`.

*   `tf.estimator`

    *   The tf.estimator API is removed.

# variable that doesn't exist. Please keep this list in alphabetical order.
#
# Find usage in scripts with e.g.:
#   cd ci/official
#   ls *.sh utilities/*.sh | xargs grep -H --color=always TFCI_ARG_HERE
# You may also get an overview, e.g.:
#   cd ci/official
#   grep -o '^TFCI\w*' envs/ci_default | xargs -n 1 -I{} bash -c "echo; echo {}; grep -R -H --exclude-dir=envs --color=always '{}'"
TFCI_ARTIFACT_FINAL_GCS_ENABLE=