TrackMetrics: Add device-based statistics for audio

Compute summary statistics based on the current device
rather than the entire AudioTrack or AudioRecord duration.

Test: adb shell dumpsys media.metrics
Bug: 149850236
Change-Id: Ia3a5707c43c4530f5a6ac90f52901bd2e0bd0bab
diff --git a/include/private/media/AudioTrackShared.h b/include/private/media/AudioTrackShared.h
index 8aec80d..9cabd8b 100644
--- a/include/private/media/AudioTrackShared.h
+++ b/include/private/media/AudioTrackShared.h
@@ -614,6 +614,8 @@
     // and thus which resulted in an underrun.
     virtual uint32_t    getUnderrunFrames() const { return mCblk->u.mStreaming.mUnderrunFrames; }
 
+    virtual uint32_t    getUnderrunCount() const { return mCblk->u.mStreaming.mUnderrunCount; }
+
     // Return the playback speed and pitch read atomically. Not multi-thread safe on server side.
     AudioPlaybackRate getPlaybackRate();