Only use payload size within the receive/send interval for bitrate probing.

webrtc/modules/congestion_controller/probe_bitrate_estimator.h

Index: webrtc/modules/congestion_controller/probe_bitrate_estimator.h
diff --git a/webrtc/modules/congestion_controller/probe_bitrate_estimator.h b/webrtc/modules/congestion_controller/probe_bitrate_estimator.h
index e6f77c034517f24f35b164fe835de8688a16f67a..c25c727dd9b995d4030da9158e82d16ad841e7ef 100644
--- a/webrtc/modules/congestion_controller/probe_bitrate_estimator.h
+++ b/webrtc/modules/congestion_controller/probe_bitrate_estimator.h
@@ -33,7 +33,9 @@ class ProbeBitrateEstimator {
     int64_t last_send_ms = 0;
     int64_t first_receive_ms = std::numeric_limits<int64_t>::max();
     int64_t last_receive_ms = 0;
-    size_t size = 0;
+    int size_last_send = 0;
+    int size_first_receive = 0;
+    int size_total = 0;
   };
 
   // Erases old cluster data that was seen before |timestamp_ms|.