Perform probing on network route change.

webrtc/modules/congestion_controller/congestion_controller.cc

Index: webrtc/modules/congestion_controller/congestion_controller.cc
diff --git a/webrtc/modules/congestion_controller/congestion_controller.cc b/webrtc/modules/congestion_controller/congestion_controller.cc
index 34b174ebc6f6c93c2ea46146ddbb5231528f3394..f3e9fc12993a480d0d9144fbb8d332f161851005 100644
--- a/webrtc/modules/congestion_controller/congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/congestion_controller.cc
@@ -233,7 +233,10 @@ void CongestionController::ResetBweAndBitrates(int bitrate_bps,
   transport_feedback_adapter_.InitBwe();
   transport_feedback_adapter_.SetStartBitrate(bitrate_bps);
   transport_feedback_adapter_.SetMinBitrate(min_bitrate_bps);

[stefan-webrtc, 2017/02/22 14:38:00]

Reading this code makes me think... What happens if we get acks from packets
sent on the previous transport after this? Should we reset the SendTimeHistory
here as well, or at least remove instances which are from the old transport
pair?

[philipel, 2017/02/23 11:57:01]

SendTimeHistory is now also cleared when ResetBweAndBitrates is called.

-  // TODO(holmer): Trigger a new probe once mid-call probing is implemented.
+
+  probe_controller_.reset(new ProbeController(pacer_.get(), clock_));
+  probe_controller_->SetBitrates(min_bitrate_bps, bitrate_bps, max_bitrate_bps);
+
   MaybeTriggerOnNetworkChanged();
 }