message: std::string -> tensorflow::tstring
diff: @@ -598,7 +598,7 @@ class BoostedTreesCalculateBestFeatureSplitV2 : public OpKernel {
  // Split types.
  const Tensor* split_types_t;
  OP_REQUIRES_OK(context, context->input("split_types", &split_types_t));
  - const auto split_types = split_types_t->vec<string>();
  + const auto split_types = split_types_t->vec<tstring>();
  DCHECK_EQ(split_types.size(), num_features_);
  // Validate.
  for (int i = 0; i < num_features_; ++i) {
  