aaudio: use xruns detected in the service

The service knows when an actual xrun occurs so we pass
that value to the client.

Bug: 38512417
Test: write_sine_callback -pl -n1 -s20 -c2 -u
Change-Id: I9e5ff1edd2e9378957309280162d7cda855f5adb
diff --git a/media/libaaudio/src/binding/AAudioServiceMessage.h b/media/libaaudio/src/binding/AAudioServiceMessage.h
index 54e8001..9779f24 100644
--- a/media/libaaudio/src/binding/AAudioServiceMessage.h
+++ b/media/libaaudio/src/binding/AAudioServiceMessage.h
@@ -38,13 +38,16 @@
     AAUDIO_SERVICE_EVENT_FLUSHED,
     AAUDIO_SERVICE_EVENT_CLOSED,
     AAUDIO_SERVICE_EVENT_DISCONNECTED,
-    AAUDIO_SERVICE_EVENT_VOLUME
+    AAUDIO_SERVICE_EVENT_VOLUME,
+    AAUDIO_SERVICE_EVENT_XRUN
 } aaudio_service_event_t;
 
 struct AAudioMessageEvent {
     aaudio_service_event_t event;
-    double                 dataDouble;
-    int64_t                dataLong;
+    union {
+        double  dataDouble;
+        int64_t dataLong;
+    };
 };
 
 typedef struct AAudioServiceMessage_s {