Address some violations of chromium-style.

webrtc/modules/congestion_controller/probe_bitrate_estimator.cc

Index: webrtc/modules/congestion_controller/probe_bitrate_estimator.cc
diff --git a/webrtc/modules/congestion_controller/probe_bitrate_estimator.cc b/webrtc/modules/congestion_controller/probe_bitrate_estimator.cc
index 2d66198ef833744eadf6c4184c00bdbc00b76ef4..a3b0b8830b3a3311864b7f97122a6dea13ea3965 100644
--- a/webrtc/modules/congestion_controller/probe_bitrate_estimator.cc
+++ b/webrtc/modules/congestion_controller/probe_bitrate_estimator.cc
@@ -43,6 +43,8 @@ namespace webrtc {
 ProbeBitrateEstimator::ProbeBitrateEstimator(RtcEventLog* event_log)
     : event_log_(event_log) {}
 
+ProbeBitrateEstimator::~ProbeBitrateEstimator() = default;
+
 int ProbeBitrateEstimator::HandleProbeAndEstimateBitrate(
     const PacketFeedback& packet_feedback) {
   int cluster_id = packet_feedback.pacing_info.probe_cluster_id;