Dead code removed plus const ref std::string to avoid copies. Bug: webrtc:7494 Change-Id: Ic408a810ae310fea942f25fc697ab81017c8a739 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/201624 Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Cr-Commit-Position: refs/heads/master@{#32968}