message: Pass by value things which gets copied.
diff: @@ -150,7 +150,7 @@ class XlaBuilder {
  // result, OpMetadata is set on the Computation Builder. All subsequent
  // instructions generated via this Computation Builder will have the same
  // OpMetadata attached until a call to ClearOpMetadata.
  - void SetOpMetadata(const OpMetadata& metadata) { metadata_ = metadata; }
  + void SetOpMetadata(OpMetadata metadata) { metadata_ = std::move(metadata); }
  // Clears the HloMetadata state.
  void ClearOpMetadata() { metadata_.Clear(); }
  