message: Give set insert a chance to be faster by using emplace().
diff: @@ -1290,13 +1290,13 @@ Signature KytheFactsExtractor::CreateScopeRelativeSignature(
  void KytheFactsExtractor::CreateFact(const VName& vname,
  absl::string_view fact_name,
  absl::string_view fact_value) {
  - kythe_data_.facts.insert(Fact(vname, fact_name, fact_value));
  + kythe_data_.facts.emplace(vname, fact_name, fact_value);
  }
  void KytheFactsExtractor::CreateEdge(const VName& source_node,
  absl::string_view edge_name,
  const VName& target_node) {
  - kythe_data_.edges.insert(Edge(source_node, edge_name, target_node));
  + kythe_data_.edges.emplace(source_node, edge_name, target_node);
  }
  std::ostream& KytheFactsPrinter::PrintJsonStream(std::ostream& stream) const {
  