This will allow downstream projects to use it to construct their own injected codecs without pulling in dependencies on software codecs that they don't need. TBR=shampson@webrtc.org Bug: webrtc:7925 Change-Id: Ie5c246bbf8e2ef1b27562887f717af9e719a1edf Reviewed-on: https://webrtc-review.googlesource.com/c/107698 Commit-Queue: Jonathan Yu <yujo@chromium.org> Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org> Reviewed-by: Anders Carlsson <andersc@webrtc.org> Cr-Commit-Position: refs/heads/master@{#25379}