Add WebRTC.BWE.MidCallProbing.* metrics.

webrtc/modules/congestion_controller/probe_controller.h

Index: webrtc/modules/congestion_controller/probe_controller.h
diff --git a/webrtc/modules/congestion_controller/probe_controller.h b/webrtc/modules/congestion_controller/probe_controller.h
index 68e98d53792988d3c3d5719f0708203ae5b795db..a4201e63b56bb58c629ef5c1991858a021ffb190 100644
--- a/webrtc/modules/congestion_controller/probe_controller.h
+++ b/webrtc/modules/congestion_controller/probe_controller.h
@@ -67,6 +67,11 @@ class ProbeController {
   int64_t last_alr_probing_time_ GUARDED_BY(critsect_);
   bool enable_periodic_alr_probing_ GUARDED_BY(critsect_);
 
+  // For WebRTC.BWE.MidCallProbing.* metric.
+  bool mid_call_probing_waiting_for_result_ GUARDED_BY(&critsect_);
+  int64_t mid_call_probing_bitrate_bps_ GUARDED_BY(&critsect_);
+  int64_t mid_call_probing_succcess_threshold_ GUARDED_BY(&critsect_);
+
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(ProbeController);
 };