message: Fix uninitialized value.
diff: @@ -1446,7 +1446,7 @@ class HloInstruction {
  string channel_name_;
  // Estimate of the duration of a host computation in nanoseconds.
  - int64 cost_estimate_ns_;
  + int64 cost_estimate_ns_ = 0;
  // Computations called by this instruction.
  std::vector<HloComputation*> called_computations_;
  