Add a placeholder stat for logging the estimated residual echo likelihood.

webrtc/api/mediastreaminterface.h

Index: webrtc/api/mediastreaminterface.h
diff --git a/webrtc/api/mediastreaminterface.h b/webrtc/api/mediastreaminterface.h
index 988ee8438361aaff2dd571fe2e79fa2907a9e14f..d2bc6480b20be9013ae0356a56eb2d0d4849e74f 100644
--- a/webrtc/api/mediastreaminterface.h
+++ b/webrtc/api/mediastreaminterface.h
@@ -206,6 +206,7 @@ class AudioProcessorInterface : public rtc::RefCountInterface {
     int echo_delay_median_ms;
     float aec_quality_min;
     int echo_delay_std_ms;

[the sun, 2016/10/19 18:27:06]

While you're poking around, why isn't echo_delay_std_ms next to
echo_delay_media_ms?

[ivoc, 2016/10/20 14:28:12]

It is now.

+    float residual_echo_likelihood = 0.0f;

[the sun, 2016/10/19 18:27:06]

Initialize all fields in the same way, please - in other words change the old
ones or add the new one to the initializer list.

[ivoc, 2016/10/20 14:28:12]

Done.

     float aec_divergent_filter_fraction;
   };