Let CreateVideoDecoder take a cricket::VideoCodec.

This makes it possible for decoder factories to actually provide any
video codec, not just the ones WebRTC knows about. It also brings
the decoder factory interface more in line with that of the encoder


Review-Url: https://codereview.webrtc.org/3007433002
Cr-Original-Commit-Position: refs/heads/master@{#19654}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: ebd4f7988eb31d7c4c2a9cf2581c77a33a0ad6c4
6 files changed