There is a race condition on reading
`ObjCNetworkMonitor::_network_monitor` field.
The `ObjCNetworkMonitor::OnPathUpdate()` checks its nullability
on the org.webrtc.RTCDispatcherNetworkMonitor thread BEFORE the
`ObjCNetworkMonitor::Start()` assigns it on the network_monitor thread.
In addition, this field is neither atomic nor protected by mutex so its
last assigned value is not guaranteed to be visible to
another [reading] thread.
Bug: webrtc:355238623
Change-Id: I1a05215111cc873b7d4931824e18f281aebfb91f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/357880
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Peter Hanspers <peterhanspers@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42778}
b8841f8ebe