message: Add GetMap method to OpNameMapper.
diff: @@ -47,6 +47,11 @@ class OpNameMapper {
  // class maintains uniqueness in a different scope.
  virtual bool IsUnique(llvm::StringRef name);
  + // Returns a constant view of the underlying map.
  + const absl::flat_hash_map<mlir::Operation*, std::string>& GetMap() const {
  + return op_to_name_;
  + }
  +
  private:
  // Returns name from the location of the operation.
  virtual std::string GetName(mlir::Operation* op) = 0;
  