message: Create global_step when recording summaries if needed
  User might have not created global_step prior to using
  some summary method.
diff: @@ -71,7 +71,7 @@ def should_record_summaries():
  def record_summaries_every_n_global_steps(n, global_step=None):
  """Sets the should_record_summaries Tensor to true if global_step % n == 0."""
  if global_step is None:
  - global_step = training_util.get_global_step()
  + global_step = training_util.get_or_create_global_step()
  collection_ref = ops.get_collection_ref(_SHOULD_RECORD_SUMMARIES_NAME)
  old = collection_ref[:]
  with ops.device("cpu:0"):
  @@ -560,7 +560,7 @@ def _serialize_graph(arbitrary_graph):
  def _choose_step(step):
  if step is None:
  - return training_util.get_global_step()
  + return training_util.get_or_create_global_step()
  if not isinstance(step, ops.Tensor):
  return ops.convert_to_tensor(step, dtypes.int64)
  return step
  