Two new classes are added to WebRTC from Chrome: ChannelMixer and
ChannelMixingMatrix but they are not yet utilized in the audio path for
WebRTC.
The idea is to utilize these new classes when adding support for multi-
channel encoding/decoding in WebRTC/Chrome.
Adds support for a new enumerator call webrtc::ChannelLayout and some
helper methods which maps between channel layout and number of channels.
These parts are also copied from Chrome.
Minor (cosmetic) changes are also done on the AudioFrame to prepare
for upcoming work.
Bug: webrtc:10783
Change-Id: I6cd7a13a3bc1c8bbfa19bc974c7a011d22d19197
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/141674
Commit-Queue: Henrik Andreassson <henrika@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28482}
