This CL also improves test coverage and fixes an issue where the
(until now) unused code path for useful padding did not respect the
lower bound packet sizes.
Bug: webrtc:8975
Change-Id: I065745ca7ac9f7098d796c6a015cd96f052ee94f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/142801
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28343}