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..e8f51cda3e2316be4882f76af3a1fadee472477c 100644
--- a/webrtc/modules/audio_processing/residual_echo_detector.h
+++ b/webrtc/modules/audio_processing/residual_echo_detector.h
@@ -37,6 +37,9 @@ class ResidualEchoDetector {
   // This function should be called while holding the capture lock.
   void Initialize();
 
+  // This function is for testing purposes only.
+  void SetReliabilityForTest(float value) { reliability_ = value; }
+
   static void PackRenderAudioBuffer(AudioBuffer* audio,
                                     std::vector<float>* packed_buffer);
 
@@ -71,6 +74,8 @@ class ResidualEchoDetector {
   MeanVarianceEstimator capture_statistics_;
   // Current echo likelihood.
   float echo_likelihood_ = 0.f;
+  // Reliability of the current likelihood.
+  float reliability_ = 0.f;
 };
 
 }  // namespace webrtc