message: Disables logging and summaries of steps, steps/s, loss etc. when RunConfig.log_step_count_steps is None.
  This is already how Estimator works (as one can see in line 2136 where we explicitly replace log_step_count_steps as None).  It should be backward compatible as current code would have crashed if log_step_count_steps is None.
diff: @@ -2480,6 +2480,7 @@ class TPUEstimator(estimator_lib.Estimator):
  # examples_hook is added to training_hooks for both CPU and TPU
  # execution.
  + if self._log_every_n_steps is not None:
  examples_hook = ExamplesPerSecondHook(
  ctx.global_batch_size,
  output_dir=self.model_dir,
  @@ -2489,6 +2490,7 @@ class TPUEstimator(estimator_lib.Estimator):
  logging.info('Running %s on CPU', mode)
  estimator_spec = model_fn_wrapper.call_without_tpu(
  features, labels, is_export_mode=is_export_mode)
  + if self._log_every_n_steps is not None:
  estimator_spec = estimator_spec._replace(
  training_hooks=estimator_spec.training_hooks + (examples_hook,))
  return estimator_spec
  @@ -2540,10 +2542,6 @@ class TPUEstimator(estimator_lib.Estimator):
  with ops.control_dependencies([loss]):
  global_step = array_ops.identity(training.get_global_step())
  hooks = input_hooks + shutdown_hooks
  - logging_hook_frequency = ( # Divide and round up
  - (self._log_every_n_steps +
  - self._config.tpu_config.iterations_per_loop - 1) //
  - self._config.tpu_config.iterations_per_loop)
  hooks.extend([
  TPUInfeedOutfeedSessionHook(
  ctx,
  @@ -2553,13 +2551,19 @@ class TPUEstimator(estimator_lib.Estimator):
  run_infeed_loop_on_coordinator),
  rendezvous=self._rendezvous[mode],
  ),
  - InstallSignalHandlerHook(),
  + InstallSignalHandlerHook()
  + ])
  + if self._log_every_n_steps is not None:
  + logging_hook_frequency = ( # Divide and round up
  + (self._log_every_n_steps +
  + self._config.tpu_config.iterations_per_loop - 1) //
  + self._config.tpu_config.iterations_per_loop)
  + hooks.append(
  training.LoggingTensorHook({
  'loss': array_ops.identity(loss),
  'step': global_step,
  },
  - every_n_iter=logging_hook_frequency)
  - ])
  + every_n_iter=logging_hook_frequency))
  examples_hook._set_steps_per_run( # pylint: disable=protected-access
  self._config.tpu_config.iterations_per_loop)
  hooks.append(examples_hook)
  