message: Add default args for Run and RunWithBorrowedArgs
diff: @@ -215,16 +215,17 @@ class InstantiatedCapturedFunction {
  // for modeling Iterator's GetNext() resource usage.
  Status Run(IteratorContext* ctx, std::vector<Tensor>&& args,
  std::vector<Tensor>* rets,
  - const std::shared_ptr<model::Node>& node) const;
  + const std::shared_ptr<model::Node>& node = nullptr) const;
  // Synchronously runs the captured function on the given `args`, and stores
  // the results in `*rets`. Prefer to use `Run()` or `RunAsync()` when
  // possible. Pass non-null `node` to record processing time for modeling
  // Iterator's GetNext() resource usage.
  - Status RunWithBorrowedArgs(IteratorContext* ctx,
  + Status RunWithBorrowedArgs(
  + IteratorContext* ctx,
  const std::vector<Tensor>& args,
  std::vector<Tensor>* rets,
  - const std::shared_ptr<model::Node>& node) const;
  + const std::shared_ptr<model::Node>& node = nullptr) const;
  // Synchronously runs the captured function on the given `args`, and stores
  // the results in `*rets`. Prefer to use `Run()` or `RunAsync()` when
  