Reland of New statistics interface for APM

webrtc/modules/audio_processing/audio_processing_impl.h

Index: webrtc/modules/audio_processing/audio_processing_impl.h
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.h b/webrtc/modules/audio_processing/audio_processing_impl.h
index aec4ed7086d992b3bcb01d154a5d49f1dc392406..eb143083011990dafbff4da283dfd136de5d2eee 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.h
+++ b/webrtc/modules/audio_processing/audio_processing_impl.h
@@ -116,6 +116,8 @@ class AudioProcessingImpl : public AudioProcessing {
   bool was_stream_delay_set() const override
       EXCLUSIVE_LOCKS_REQUIRED(crit_capture_);
 
+  AudioProcessingStatistics GetStatistics() const override;
+
   // Methods returning pointers to APM submodules.
   // No locks are aquired in those, as those locks
   // would offer no protection (the submodules are