This is to satisfy a thread checker in AudioSendStream.
Bug: webrtc:9510
Change-Id: I5ba03562fcdc3e93d77707e41220b82b99581470
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/169343
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30648}