Add AEC filter divergence metric to StatsCollector.

webrtc/api/statscollector.cc

Index: webrtc/api/statscollector.cc
diff --git a/webrtc/api/statscollector.cc b/webrtc/api/statscollector.cc
index 0901fc61b1e0a134cd4a817c630e31e38c69c715..38fb5fb7db19f17c4fe2b935624478d9f1f28c55 100644
--- a/webrtc/api/statscollector.cc
+++ b/webrtc/api/statscollector.cc
@@ -937,6 +937,9 @@ void StatsCollector::UpdateReportFromAudioTrack(AudioTrackInterface* track,
         report, stats.typing_noise_detected, stats.echo_return_loss,
         stats.echo_return_loss_enhancement, stats.echo_delay_median_ms,
         stats.aec_quality_min, stats.echo_delay_std_ms);
+
+    report->AddFloat(StatsReport::kStatsValueNameAecDivergentFilterFraction,
+                     stats.aec_divergent_filter_fraction);
   }
 }