This new parallel GetStatistics function uses Optionals to indicate if stats are valid or not, and no longer relies on default values. It also takes an argument to indicate if receive streams are present, and if not several stats will not be set. Bug: b/67926135 Change-Id: I175de1c65c414bea6ec9ca8b0b16f07cb2308d9f Reviewed-on: https://webrtc-review.googlesource.com/17942 Commit-Queue: Ivo Creusen <ivoc@webrtc.org> Reviewed-by: Per Kjellander <perkj@webrtc.org> Reviewed-by: Henrik Boström <hbos@webrtc.org> Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org> Cr-Commit-Position: refs/heads/master@{#20789}