The whole point of all the audio codec stuff we've recently published
in api/ is to function as lego bricks so that building stuff like our
builtin audio codec factories will be easy.
(This has landed once before, but got reverted because of Chromium test
failures---apparently, someone isn't ignoring the case of the codec names
like they're supposed to. The quick fix was to preserve the same case
used by the old implementation.)
BUG=webrtc:7821, webrtc:7822
Review-Url: https://codereview.webrtc.org/2998263002
Cr-Commit-Position: refs/heads/master@{#19512}
e5eb7247ff