The race occurs if the transport is being destroyed at the same time as
a callback occurs on the usrsctp timer thread (for example, for a
retransmission). Fixed by slightly extending the scope of mutex
acquisition to include posting a task to the network thread, where it's
safe to do further work.
Bug: chromium:1162424
Change-Id: Ia25c96fa51cd4ba2d8690ba03de8af9e9f1605ea
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/202560
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Taylor <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33048}