WebRtcVoiceCodecs: Eliminate some useless copying

Review-Url: https://codereview.webrtc.org/2067453002
Cr-Original-Commit-Position: refs/heads/master@{#13151}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: edaa849013ad321779fa1069e49bd99fbc6e5433
1 file changed