This makes Environment and thus field trials a required parameter, thus RemoteBitrateEstimators member no longer need to fallback to the global field trial string. Bug: webrtc:42220378 Change-Id: Ieb6ff442d5fde5fa9715573c758a7e078f0ceea4 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/349922 Commit-Queue: Danil Chapovalov <danilchap@webrtc.org> Reviewed-by: Per Kjellander <perkj@webrtc.org> Cr-Commit-Position: refs/heads/main@{#42314}