message: Return ComputationLayout as a reference from the HLO module.
diff: @@ -103,7 +103,7 @@ class HloModule {
  return config_.mutable_entry_computation_layout();
  }
  - ComputationLayout entry_computation_layout() const {
  + const ComputationLayout& entry_computation_layout() const {
  return config_.entry_computation_layout();
  }
  