MediaMetrics: Track AudioTrack and AudioRecord callers

Test: adb shell dumpsys media.metrics
Bug: 149850236
Bug: 153658358
Change-Id: If2b0a792cf4cc6c5b125513861b3dfb257bb3cbe
diff --git a/media/libaaudio/src/legacy/AudioStreamLegacy.h b/media/libaaudio/src/legacy/AudioStreamLegacy.h
index cd5eb5a..9c24b2b 100644
--- a/media/libaaudio/src/legacy/AudioStreamLegacy.h
+++ b/media/libaaudio/src/legacy/AudioStreamLegacy.h
@@ -129,6 +129,7 @@
     }
 
     // This is used for exact matching by MediaMetrics. So do not change it.
+    // MediaMetricsConstants.h: AMEDIAMETRICS_PROP_CALLERNAME_VALUE_AAUDIO
     static constexpr char     kCallerName[] = "aaudio";
 
     MonotonicCounter           mFramesWritten;