Handle BW drop in ALR region and initiate probing

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 4cf34c3c8707c417657055afee4560c28883a7ab..efcc2a1d4a39ab27ebdf10e22d91a4484d64ebf3 100644
--- a/webrtc/modules/congestion_controller/probe_controller.h
+++ b/webrtc/modules/congestion_controller/probe_controller.h
@@ -53,6 +53,7 @@ class ProbeController {
   int64_t time_last_probing_initiated_ms_ GUARDED_BY(critsect_);
   int estimated_bitrate_bps_ GUARDED_BY(critsect_);
   int max_bitrate_bps_ GUARDED_BY(critsect_);
+  int64_t last_alr_probing_time_ GUARDED_BY(critsect_);
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(ProbeController);
 };