Add AEC filter divergence metric to StatsCollector.

webrtc/api/mediastreaminterface.h

Index: webrtc/api/mediastreaminterface.h
diff --git a/webrtc/api/mediastreaminterface.h b/webrtc/api/mediastreaminterface.h
index 2a3f3473b021172b4e7bc17c92b7bb49ba370c6e..57c0776a322f56e6761e00d77a8b4c8735a38d4b 100644
--- a/webrtc/api/mediastreaminterface.h
+++ b/webrtc/api/mediastreaminterface.h
@@ -215,7 +215,8 @@ class AudioProcessorInterface : public rtc::RefCountInterface {
                             echo_return_loss_enhancement(0),
                             echo_delay_median_ms(0),
                             aec_quality_min(0.0),
-                            echo_delay_std_ms(0) {}
+                            echo_delay_std_ms(0),
+                            aec_divergent_filter_fraction(0.0) {}
     ~AudioProcessorStats() {}
 
     bool typing_noise_detected;
@@ -224,6 +225,7 @@ class AudioProcessorInterface : public rtc::RefCountInterface {
     int echo_delay_median_ms;
     float aec_quality_min;
     int echo_delay_std_ms;
+    float aec_divergent_filter_fraction;
   };
 
   // Get audio processor statistics.