a990784da3
Change internal indexing of registered decoders. It makes sense because payload type is unique, while ACM codec ID may not be. This is a step towards allowing for addition of external decoders. R=kwiberg@webrtc.org Review URL: https://webrtc-codereview.appspot.com/44869004 Cr-Commit-Position: refs/heads/master@{#8867}