Along the way slightly simplify the class interface since views carry audio properties. Also, now allocating FrameCombiner allocates the mixing buffer in the same allocation. Bug: chromium:335805780 Change-Id: Id7a76b040c11064e1e4daf01a371328769162554 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/352502 Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org> Reviewed-by: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/main@{#42465}