message: Make node const in tensorflow::OutputTensor
diff: @@ -261,10 +261,10 @@ class Node {
  // that a single `OutputTensor` can correspond to multiple `Edge`s if the output
  // is consumed by multiple destination nodes.
  struct OutputTensor {
  - Node* node;
  + const Node* node;
  int index;
  - OutputTensor(Node* n, int i) : node(n), index(i) {}
  + OutputTensor(const Node* n, int i) : node(n), index(i) {}
  OutputTensor() : node(nullptr), index(0) {}
  };
  