This means that we avoid exposing FakeNetworkSocket and
moves related code closer together.
It's done in preparation for future work on simulated time testing.
Bug: webrtc:9883
Change-Id: Id6d1b0a6055f30da8e6646bd5347024fbd9c9dfd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/164537
Reviewed-by: Jonas Olsson <jonasolsson@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30181}