This reverts commit f8da43d179043f1df2e1c3e2c49494bc23f4ec28. Reason for revert: Appears to break downstream app. Original change's description: > Replace RecursiveCriticalSection with Mutex in RTCAudioSession. > > Bug: webrtc:11567 > Change-Id: I2a2ddbce57d070d6cbad5a64defb4c27be77a665 > Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/206472 > Reviewed-by: Harald Alvestrand <hta@webrtc.org> > Reviewed-by: Kári Helgason <kthelgason@webrtc.org> > Commit-Queue: Niels Moller <nisse@webrtc.org> > Cr-Commit-Position: refs/heads/master@{#33259} TBR=nisse@webrtc.org,kthelgason@webrtc.org,hta@webrtc.org,handellm@webrtc.org Change-Id: Id9a97068722c7c72fc5d21102298249fd7a7cd9a No-Presubmit: true No-Tree-Checks: true No-Try: true Bug: webrtc:11567 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/207431 Reviewed-by: Niels Moller <nisse@webrtc.org> Commit-Queue: Niels Moller <nisse@webrtc.org> Cr-Commit-Position: refs/heads/master@{#33268}