This is a revert of the revert of commit d729d12454906d924d5a142deb3432
which was reverted because it caused upstream test failures.
Contains fix in StreamScheduler::GetActiveStreamsForTesting.
This reverts commit 5df960d3073630c5619e00d79f89937bf6fabd69.
Bug: webrtc:5696
Change-Id: I89dada257a6fb1f149f50067ab66b17e24a7c01a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/266368
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37299}