This is needed in the general case, now that we aim to support codecs other than those built-in to WebRTC. BUG=webrtc:8159 Change-Id: I40a41252bf69ad5d4d0208e3c1e8918da7394706 Reviewed-on: https://webrtc-review.googlesource.com/5380 Commit-Queue: Karl Wiberg <kwiberg@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20136}