This change replaces the use of sync_label from StreamParams with
the new stream_labels() and set_stream_labels() getter and setter.
Bug: webrtc:7932
Change-Id: Ibd6d38f7d4efed37ac07963e6fbe377c93a28fd6
Reviewed-on: https://webrtc-review.googlesource.com/58540
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22257}