message: Remove underscore prefix from _concat.
diff: @@ -100,8 +100,8 @@ bool IsOpWithUnderscorePrefix(const string& s) {
  "fused_batch_norm", "histogram_fixed_width", "stack",
  "batch_norm_with_global_normalization",
  // TODO(annarev): replace these ops in the next change.
  - "broadcast_gradient_args", "concat", "enter", "histogram_summary",
  - "ref_enter", "ref_identity", "scalar_summary"});
  + "broadcast_gradient_args", "enter", "histogram_summary", "ref_enter",
  + "ref_identity", "scalar_summary"});
  return kUnderscoreOps->count(s) > 0;
  }
  