Add some info about monopipe depth

Log the size of the playback and record threads' monopipes

Bug: 196060611
Bug: 196071180
Test: adb shell dumpsys media.audio_flinger
Change-Id: Ica0d07ca8379842fe2136de330ec123de33b66ed
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index 38e55a3..9cf457a 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -684,6 +684,7 @@
                 audio_utils::Statistics<double> mIoJitterMs{0.995 /* alpha */};
                 audio_utils::Statistics<double> mProcessTimeMs{0.995 /* alpha */};
                 audio_utils::Statistics<double> mLatencyMs{0.995 /* alpha */};
+                audio_utils::Statistics<double> mMonopipePipeDepthStats{0.999 /* alpha */};
 
                 // Save the last count when we delivered statistics to mediametrics.
                 int64_t                 mLastRecordedTimestampVerifierN = 0;