Add information about microphone gain changes to AEC3

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 4e25f15e36289c56cbc0f9a92d80d07e77f95f93..37b15c28935f29cb6450f5f5cec3d53fe640f50f 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.h
+++ b/webrtc/modules/audio_processing/audio_processing_impl.h
@@ -366,6 +366,8 @@ class AudioProcessingImpl : public AudioProcessing {
     // tracked by the capture_audio_.
     StreamConfig capture_processing_format;
     int split_rate;
+    int previous_agc_level;
+    bool echo_path_gain_change;
   } capture_ GUARDED_BY(crit_capture_);
 
   struct ApmCaptureNonLockedState {