Add a reliability term to the echo detector.

webrtc/modules/audio_processing/residual_echo_detector.h

Index: webrtc/modules/audio_processing/residual_echo_detector.h
diff --git a/webrtc/modules/audio_processing/residual_echo_detector.h b/webrtc/modules/audio_processing/residual_echo_detector.h
index 37aa283b0869487e08a498961e292667f458c71e..0b964399489d494a95ef4caffccf56b1a09e7c20 100644
--- a/webrtc/modules/audio_processing/residual_echo_detector.h
+++ b/webrtc/modules/audio_processing/residual_echo_detector.h
@@ -71,6 +71,8 @@ class ResidualEchoDetector {
   MeanVarianceEstimator capture_statistics_;
   // Current echo likelihood.
   float echo_likelihood_ = 0.f;
+  // Reliability of the current likelihood.
+  float reliability_ = 0.f;
 };
 
 }  // namespace webrtc