This CL only includes the necessary changes in PhysicalSocketServer,
and doesn't include the Java or Objective C API.
Note that this is doing exactly the same thing as UDPSocketPosix
in chromium.
BUG=webrtc:5658
Change-Id: I295455eaccba2a83cdd1bc55848f325c310f8d32
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168260
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Commit-Queue: Taylor <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30478}