All decoders are injectable, no need to create built-in codecs from there. Bug: webrtc:7925 Change-Id: Iabf3d59a8e4d721ad29386acbf138b7e5992ce5e Reviewed-on: https://webrtc-review.googlesource.com/72441 Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Commit-Queue: Anders Carlsson <andersc@webrtc.org> Cr-Commit-Position: refs/heads/master@{#23397}