Further work on libmediametrics stable API

implement a missing method (for inflight metrics), enumerate exported
symbols.

Bug: 119675363
Test: build, CTS media/codec tests
Change-Id: Id92f1b331babacc0de6c0005d6ba0c97c91c0291
diff --git a/media/libmediametrics/libmediametrics.map.txt b/media/libmediametrics/libmediametrics.map.txt
new file mode 100644
index 0000000..c46281a
--- /dev/null
+++ b/media/libmediametrics/libmediametrics.map.txt
@@ -0,0 +1,29 @@
+LIBMEDIAMETRICS_1 {
+  global:
+    mediametrics_addDouble; # apex
+    mediametrics_addInt32; # apex
+    mediametrics_addInt64; # apex
+    mediametrics_addRate; # apex
+    mediametrics_count; # apex
+    mediametrics_create; # apex
+    mediametrics_delete; # apex
+    mediametrics_freeCString; # apex
+    mediametrics_getAttributes; # apex
+    mediametrics_getCString; # apex
+    mediametrics_getDouble; # apex
+    mediametrics_getInt32; # apex
+    mediametrics_getInt64; # apex
+    mediametrics_getKey; # apex
+    mediametrics_getRate; # apex
+    mediametrics_isEnabled; # apex
+    mediametrics_readable; # apex
+    mediametrics_selfRecord; # apex
+    mediametrics_setCString; # apex
+    mediametrics_setDouble; # apex
+    mediametrics_setInt32; # apex
+    mediametrics_setInt64; # apex
+    mediametrics_setRate; # apex
+    mediametrics_setUid; # apex
+  local:
+    *;
+};