Call OnSentPacket for all packets sent in the test framework.

Required a bit of refactoring to make it possible to pass a Call to DirectTransport on construction. This also lead to me having to remove the shared lock between PacketTransport and RtpRtcpObserver. Now RtpRtcpObserver has a SetTransports method instead of a SetReceivers method.

BUG=webrtc:4173

Review URL: https://codereview.webrtc.org/1419193002

Cr-Original-Commit-Position: refs/heads/master@{#10430}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f116bd0d7a3cdad20bb638d5a87427bd920c8904
16 files changed