This is a reland of 6b9c60b06d
Original change's description:
> Removes lock release in PacedSender callback.
>
> The PacedSender currently has logic to temporarily release its internal
> lock while sending or asking for padding.
> This creates some tricky situations in the pacing controller where we
> need to consider if some thread can enter while we the process thread is
> actually processing, just temporarily busy sending.
>
> Since the pacing call stack is no longer cyclic, we can actually remove
> this lock-release now.
>
> Bug: webrtc:10809
> Change-Id: Ic59c605252bed1f96a03406c908a30cd1012f995
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173592
> Reviewed-by: Sebastian Jansson <srte@webrtc.org>
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31206}
Bug: webrtc:10809
Change-Id: Id39fc49b0a038e7ae3a0d9818fb0806c33ae0ae0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/175656
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31332}
b46df3da44